We can’t recover the first password, or any other password.
Once the files are encrypted, nothing really happens to them so they should open today if you’re providing the right password. We have only one sign in from you on that day before your vacation, so it seems you did not in fact enter the password more than the three times that are necessary for the sign up process.
There are also several layers here – when you tried to sign in today, and failed, you issued a password reset. Then you can sign in to the app and the account. When you try to open a encrypted file, that was encrypted with the old password, you’ll get a prompt for a “file password”. Now you get a new chance to enter the right password. If that doesn’t work either, the chances really are that you either wrote the wrong thing, or you’re misreading it now, or you mistyped originally.
It seems very unlikely that the two quite independent processes of signing up and setting a password for the account, and then encrypting files using the password just set, would err in the same way at the same time for one single user. We have very, very many users who do this every day.
Occams razor applies here, I’m pretty sure you’re not entering the same password as you did originally. Sorry, I know you don’t like to hear this, but…
I suggest you try to consider just what could have gone wrong with the password typing / noting down / reading back process – and try to adjust for that.