OK, should be fixed now. Earlier today, I added lat/long to the token that gets sent back by SSO. Now, for reasons I can’t ascertain, the SSO server decided that it should switch from sending a claim with a field called UserID to a claim called userid (lowercase).
There’s no obvious reason such a thing would occur and there’s nothing I’ve done to edit any of those fields, but I managed to work out where it was coming from and remove that - but that selection has been in place for years, so unsure why it would suddenly change (other than I added unrelated claims to the token earlier today). Anyway, logging in/out will immediately fix it, or you can wait for 5 minutes for the token to expire and a refresh of it with SSO to occur.