Profile Sync not working

I'm logged into Edge using my M365 Business Standard account. Sync was working fine at one point, but lately I'm seeing this:

When I re-enable it, it stays stuck at "Not syncing". When I try to reset the sync, the reset dialog just spins endlessly (I've left it for hours) and when I re-open Edge it's still "Not syncing". Below is the output from edge://sync-internals/:

How can I resolve this? I've tried troubleshooting the service endpoints as per the documentation, but the guidance isn't clear (see my issue here).