You had mentioned “Somehow or other my login password got changed; I’ve no idea how that happened.” , AxCrypt will not change sign in password automatically. You might be confused with sign in password and file password.
AxCrypt 1.x works with different passwords for each files. That means, we can assign passwords for each encrypting files. But AxCrypt 2.x use a single sign on model where the same password is used to sign in to our servers and to protect your files.
If the file was encrypted with a different password than your sign in password then you have to enter the file password(which was used to encrypt the files) while viewing/decrypting the encrypted file.
For example: AxCrypt will ask the user to enter the password when the file was encrypted by some other AxCrypt accounts’ password or user account’s old password.
Actually, without user request, AxCrypt will not change the user accounts password. So you might be manually changed the account password or confused with the file password.
Anyway, its good to know now everything works well.