Certain workstation agents are no longer auditing - Log error "Unable to connect to the Active Administrator Foundation service"
The issue is with computers that are on a different sub-net than the Active Administrator server, and using a site to site VPN.
The server has two (NIC) Network Interface Cards, and one of them are missing the Default gateway IP address.
Add the Default gateway IP address.
Within the Active Administrator console, browse to Security & Delegation | User Logon Activity
Refresh page and the workstation events should appear.
Also, under Auditing & Alerting | Audit Reports | User Logon Activity, you can refresh the report to view the User Logon Activity.