Last time with the V10 update, we resolved the issue by rebooting our router, which it turns out got us a new IP address.
With V11 update, we had to use a VPN client to present a new local IP address to the server.
It appears to me that the server-side is keeping our IP in some table which corrupts between version updates. The work-around is to get a different local IP.
Ultimately they need to flush a routing table somewhere or find where the local IP is cached.