1. Let's be clear what we're talking about: it's the Voynich manuscript, written in an unknown script, for an unknown language, a popular puzzle for linguists/codebreakers.
https://en.wikipedia.org/wiki/Voynich_manuscript

2. Proto-Romance cannot by definition be "discovered", because it is the linguistic hypothesis linking the modern Romance languages. Early Italian, or Late Latin, or Pre-Romance, or whatever you want to call it could be discovered, and to some degree this is just a terminological issue, but at the same time there is a good reason to not believe a real "Proto-Romance" ever existed: Latin was already geographically split by that point, such that although the different dialects/languages remained in contact and mutually intelligible to some degree, part of their development was independent drift rather than strictly coming from a single ancestor "Proto-Romance". From a comparative perspective it is useful to discuss that idealized proto-language, but it is idealized.

3. Various explanations for the manuscript have been proposed; none are accepted. Among other things, it may be a natural language:
https://en.wikipedia.org/wiki/Voynich_manuscript#Natural_language
But as written there on Wikipedia it does not appear to be Indo-European or Romance in particular.

4. The manuscript is much older than Proto-Romance. Dating Proto-Romance literally is tricky (see above), but let's say it's between 2000-1500 years ago. The manuscript is only about 600 years old. That would mean that it is a copy of a much earlier text, which is not impossible, but certainly should not be a default assumption.

5. Mixing of "Proto-Italic" and "Proto-Romance" scripts (I'm not sure what that means conceptually!) makes very little sense, mostly in terms of a timeline: the Latin alphabet was well established by the relevant time. Perhaps the author intentionally obfuscated the text, but why?

6. Many other proposals have been made, just to take one example:
https://ellisnelson.com/2012/08/02/ms-408-the-voynich-manuscript-mystery/
If the current proposal is indeed correct and better than the others, and it is Proto-Romance, then it should be very easy to decipher and translate transparently, without any room for uncertainty. If you really believe this, then you should simply translate the whole manuscript, publish it online, and become famous.

7. Some of the short paragraphs translated in the linked papers appear to be convincing. However, the "Vulgar Latin" is not clear to me (I've studied Latin and can read Italian, Spanish, French, and other Romance languages), and rather than try to guess about this myself, I'd like to see interlinear morpheme-by-morpheme glosses consistent with current publication standards, or at least word-by-word glossing so I don't have to line it up, and to show that the author is not just guessing about plausible meanings but actually translating the text.
It is absolutely important that there is a systematic interpretation rather than guessing, and I am at this point still skeptical.

8. Quite a few aspects of these papers suggest non-standard research. For example, the term "transliteration" refers to changing the writing system of a text but not translating the meaning, but it appears in one of the papers for what is clearly a translation (meaning interpretation in English).

9. If this is a big deal, then it should be making headlines, rather than being shared in its current form. There are many experts in Romance Linguistics, Latin Linguistics, Historical Linguistics, etc., who could verify this if given the chance. It might take some convincing (because so many similar claims have been made), but if this really is the answer, then there should be no serious difficulty getting it verified.

10. Making sweeping claims without providing sufficient, thorough evidence is usually less effective than making more specific claims. (For example, perhaps some of the glyphs in the script really are from ancient Italy, and that hypothesis might be correct regardless of the other points.) Your claims might be taken more seriously by researchers in the field if presented in that way, from the bottom up, rather than top down with the very controversial conclusion presented as the title. On the other hand, in the case of deciphering a manuscript and translating and unknown script/language, a full systematic translation could be the convincing, as mentioned above.

If you want these claims to be taken seriously, I strongly suggest either starting small and finding ways to demonstrate scientifically (which often means slowly!) some of the smaller points, building up to any conclusion. Or leap ahead yourself and then show the rest of us what we're missing once you've fully deciphered the language and can prove it transparently.

One mustn't be beguiled by the 'Voynich' mythology, which is exactly why the manuscript is referred to here only as MS408. After all, if MS408 had been discovered only last week then the solution would be received without any fuss, as it is only the mythology amassed over time that now elevates expectation. Moreover, that mythology is based entirely on not finding the solution.

Voynich is the name of the person who owned the manuscript at one point, not a myth at all. No less factual than that it currently is found at Yale, or that it is numbered 408.
The more substantial point is that it has received a lot of attention from researchers-- both professional and hobbyists-- for years, and no one has solved it yet. That means it's a hard problem. That's why you can't just detach this from that history as if it's a simple problem and refer to it vaguely as "MS 408".

The saying goes that Edison didn't fail repeatedly, he just found 2,000 ways not to make a lightbulb. Let's apply that here: considering the history, we know a lot about this manuscript, at least which hypotheses don't seem to work out and why (that's important!). With your "forget about the mythology" approach you're basically saying "forget about those 2,000 ways that don't work, and let's start over from the beginning pretending it's a new idea and hoping it works without knowing anything about those previous attempts". That's literally the opposite of science.

The first paper explains the writing system and the second paper provides demonstrable proof, as virtually all of the translated words have precisely no ambiguity.

Please provide interlinear glossing that shows this transparently. Let me interpret the meaning for myself and see if it seems plausible. The current papers do not meet basic standards for current linguistics research-- interlinear glossing is crucial for any language not known to the reader. It is concerning that the presentation of this hypothesis does not meet those standards. It doesn't mean you're wrong, but it could be presented in a much more convincing way.

Many southern European scholars are now using the solution to research the manuscript as they could intuitively see that it was correct, being Romance speakers, so that ship has already sailed.

Please link me to some reactions-- scholarly articles, reviews/responses, even blog posts, from scholars who accept this interpretation as fact. Maybe you're right! But accept my skepticism for now. If it's as big a discovery as this, then my skepticism won't matter later anyway.

Thus, the real value of MS408 lies in the linguistic information it imparts regarding the evolution of the Romance languages and the Italic alphabet. It also contains some very interesting historical information.

Absolutely. But without either redoing your research from your papers, and without having the translation process be much more transparent, I can only take your word for it.

There are various ways to verify this, some of which I described above. The best way is replication, a critical step in science: have a third party verify that your method works, and show that they can read the manuscript that way. Or, if you want to arrange this yourself, have a side-by-side translation by two research assistants, who later compare their notes to see if they reached the same translation. (Obviously that only works if you have a "new" passage, for which they do not know the translation beforehand. Pick a page at random, and see what they come up with.)

If you are the only person who can read the manuscript, then something is wrong. If not, I would welcome evidence to that effect. You picked a difficult puzzle to solve, and one that also comes with a higher burden of proof because so many others have tried it before.

If I'm being too difficult and skeptical here, I apologize, and it should easy to show that is the case.

Having read the replies it becomes apparent that I need to explain scientific protocol. That is to say: I have presented a new paradigm and solution. Thus, it is now up to others to test the paradigm and solution without me in the room: i.e. to independently verify. I can see no evidence that anyone has even attempted this. Furthermore, it should always be done entirely dispassionately.

Besides which, and I repeat, many southern European scholars have already kindly done so and they are now using the solution to translate the manuscript for their own fields of research.

Lastly, did it never occur that someone would eventually work it out?
It was merely a matter of applying rational logic in combination with prior knowledge of linguistics and historical context.