Why do app-specific passwords expire?
I set up my Thunderbird email with an app-specific password. A few days later, it has expired. Why?
Windows, Windows 6
Question marked as
Did you change your main apple ID password?
That's the only reason I can think of that would make it expire. unless you specifically revoked that password.
Using app-specific passwords - Apple Support
Any time you change or reset your primary Apple ID password, all of your app-specific passwords are revoked automatically to protect the security of your account. You'll need to generate new app-specific passwords for any apps that you want to continue using.
If that's not the case I do not know. Might want to check with apple if so:
Contact Apple for support and service - Apple Support