Hi John Powell, I know how frustrating this is especially when the same account works elsewhere but refuses to sync on this one PC. You’ve already put real effort into sorting it out and its completely understandable to feel stuck.
To fix the domain has shifted error first confirm Autodiscover and server details using Outlook AutoConfiguration and Connection Status tools then clear cached credentials and DNS, create a fresh Outlook profile rebuild the OST file verify Autodiscover points to the correct endpoint and remove any local blockers like firewall or outdated registry entries if the domain was recently moved.
On the affected PC what exact Autodiscover endpoint and server names appear in Outlook Test email Auto Configuration and Connection Status windows and how do they differ from a device where the account works?
Best regards
Lucky Charm