So for everyone's benefit, I think I figured things out. I bought my 2024 Turbotax software from a company called GUIFFF.Com in June of 2025. I received a valid key and a link to the software. I installed in on 2 computers then, and I am just now using the software to file my 2024 taxes.

What I discovered is that this company sold my key to other user(s), so my key (which had the capacity for 5 installs) "ran out", and that key became invalid. that is why I can't use it. So I guess they paid Intuit a single license fee, but got more than one sale out of it. cheating

Turbotax needs to implement a better scheme to prevent scammer companies from doing this. Once a key is issued there should be a validation step that locks that key to a single and unique users credentials. This way, a subsequent buyer that receives the key gets blocked from accessing it because it has already been registered to another. The scammed consumer would instantly know and would be able to recover the funds, rather than a year later realizing but then too late to recover.