From what I know, the main issue is that the Linear A script corpus is rather small. Another commenter here said it's only 7500 symbols in total, spread around 1500 inscriptions (so on average 5 symbols per inscription).

The other thing I find odd, however, is that it's found to be a Semitic language. If it's a Semitic language, I would have expected it to already have been deciphered. And certainly linguists would have already looked at Semitic languages, and looked hard.

Also if it were a Semitic language, why wasn't it consonantal but had vowels? Usually Semitic languages (and Egyptian maybe) write only the consonants because their stems are made three consonants and vowels are interweaved to make words.

Example semitic root K-T-B and how vowels are added in-between to form words:

kataba – He wrote yaktubu – He writes / is writing kitāb – A book kutub – Books kātib – A writer / scribe / clerk maktūb – Written / fate maktab – An office / desk maktabah – A library / bookstore

And another such root - D-R-S which means "studying" or "learning."

darasa – He studied yadrusu – He studies / is studying dirāsah – A study / school course dāris – A student / learner madrūs – Studied / carefully planned madrasah – A school

This system of triliteral roots is the reason why usually Semitic languages don't use vowels. Why would Linear A have consonant+vowel syllabary if it were semitic?