Tuesday, August 4, 2015

Windows Process Activation Service (WAS) encountered a failure when it started a worker process to serve the application pool.

If there are GPO in place, you should make sure service accounts have Log on as a Batch Job permissions

Because of this STS Token service - SecurityTokenServiceApplicationPool will not run or keeps stopping.
Central Admin site application pool keeps stopping

You will see the following error in the event log -

Windows Process Activation Service (WAS) encountered a failure when it started a worker process to serve the application pool.