Hi @Mavlyudov, thanks for messaging the Community!
It sounds like this account wasn't accessed for over 12 months. If this was the case, then the account would've been deactivated by Dropbox due to inactivity.
Once this has happened, it wouldn't be possible to recover the account or the files within.
I'm sorry to be the bearer of bad news. If there's any additional information you need, please let me know.