I'm a long-time user of Authy for 2FA on many of my Internet-based accounts. Authy has a cool feature whereby you can use it across multiple devices, with the help of a backups password. This has worked well for a couple of years, using an iPhone app, iPad app, and a Chrome desktop app on Windows 10.
Yesterday and today I added 4 new accounts using the iPhone app - that all works fine on the iPhone and I can see the OTP codes. But when I tried to see the OTP codes for those 4 accounts using the Chrome desktop app, it challenged me for the backups password (but not for the many older accounts). Then it refused to accept the backups password stored in my password manager. Even though the backups password is correct, and hasn't changed since it was created.
So I used the iOS app to change the backups password. That was successful.
Now when I launched the Chrome desktop app, it recognised that the backups password had changed and prompted me for the new password. When I entered that, it said "successful" and then re-encrypted the accounts locally. But it still has the same problem - each of those 4 new accounts needs entry of the new backups password, but the app rejects the password that it had previously accepted.
I've raised a support ticket with Authy, but checking here to see if an Authy user has seen this issue before and solved it. Google isn't much help, but I can see that somebody has experienced something that looks almost identical.