Requests to services running in the shared instance pool result in the 500 wait timeout error after rebooting Windows Server.

Workaround

• Navigate to ArcGIS Server Administrator API and restart the DynamicMappingHost Service to resolve the issue.
• Adjust the number of shared instances per machine in ArcGIS Server Manager by navigating to Site > Settings > Pooling to resolve the issue, as this restarts the DynamicMappingHost service.
• Start Portal for ArcGIS 10 minutes before ArcGIS Server - if Portal is accessible when ArcGIS Server starts the problem will not occur. This can be automated with something like powershell

Steps to Reproduce