Macs loose connection after all being fine for weeks/months.

Options

So I have 30+ Macs all setup fine with TeamViewer and My Dashboard etc.

Some on v12 some on v13.

All was working fine.

Nothing has changed on the Macs, no updates, no network changes, all fixed IPs access to the offices, VPN and Apple Remote Desktop work fine still [as a comparison network connection service] ...

Now randomly many Macs on setup TeamViewer are no longer accesible and the loose their linked Account access status.

Why?