Unknown error when signing into Apple ID

Hi

Just ran migration assistant on my brand new iMac (for the 2nd or 3rd time), and I can no longer log in to iCloud/apple ID.

I get "unknown error occurred" when i try to login, and when I try to change a Photos iCloud setting, I get com.accounts. error 10002. (please see attachments).

I TRIED IT IN SAFE MODE - SAME PROBLEM :(

Please help!

Thanks.

[Image Edited by Moderator to Remove Personal Information]