Project Server 2013: Queue Jobs hung on "Waiting To Be Processed" after provisioning PWA instance

After recently provisioning a PWA instance based on the restored content DBs of an instance from another farm, I noticed the job queue was hung with all jobs having the status of "Waiting To Be Processed". If the issue still exists after performing a simple restart of the Microsoft Project Server Queue Service 2013 service, it can be fixed most of the time by using PowerShell.

1. $serviceapp = get-spserviceapplication | ? {$_.TypeName -like "*Project*"}
2. $pwainstances = $serviceapp.Sitecollection
3. $pwainstances

You will see the details of each PWA instance in your farm. For the instance experiencing the issue, the IsOnline status should be False, as shown in the screenshot below.

This status means that the PWA instance was not provisioned correctly and is not completely online.

Resolution: Re-Provision the PWA instance in-place using PowerShell.

4. Upgrade-SPProjectWebInstance -Identity "http://url/pwa"
5. Type "y" to confirm and hit Enter.

When done, you should see the following message: Upgrade of single project site completed.

6. $pwainstances

IsOnline status should now be True.

The job queue will automatically resume to normal operation.