icloud – Messages and FaceTime apps don’t log in macOS Big Sur

Since the Big Sur Betas, I haven’t been able to log in to messages or FaceTime on my MacBook. When I open either app, the login screen appears, I log in, for a while it appears that I’ve logged in successfully, and then the login prompt reappears. Up until now I have restarted my laptop, ran several software updates, and even reinstalled macOS from the recovery menu, to no positive effect. I have also ensured I have RW permissions to ~/Library and all its subfolders. I filed an issue with the Apple Feedback app (FB8615473), but haven’t seen a response since I first filed it in September 2020.

This issue only happens for Messages and FaceTime. Finder (iCloud), photos, music, pages etc all have no problems syncing with my iCloud. I have tried removing iCloud from my Mac in system preferences and adding it back, and all that caused is a lot of headache with Documents syncing, but no help with messages, leading me to believe that Messages and FaceTime have their own authentication method separate from the system iCloud login.

I have captured one of the failed login attempts in the Console apps and a screenshot of what looks to me like relevant log messages is attached. It seems like auth for Messages is managed by some identityserviced process, which fails to generate some path (possibly a keychain storage space, I really don’t know) for the messages app.

I get no errors and iMessage works like a charm across my iPhone, iPad and Apple Watch. Handoff features including app handoff and clipboard sync also work fine between my Mac and all my other devices. I’d appreciate any help anyone could give me. Thanks a lot!

Screenshot of console logs of messages login