There was an unexpected server reboot for our applications server and our service application features were failing. On checking, I noticed the below error in the Windows Event Viewer
Event ID: 8306
An exception occurred when trying to issue security token: The HTTP service located at http://localhost:32843/SecurityTokenServiceApplication/securitytoken.svc/actas is too busy.
On browsing to http://localhost:32843/SecurityTokenServiceApplication/securitytoken.svc , I got the below error
Identify the application pool for the Service Applications.
Application Pool -> Check Status -> Start