If executions for one Hardware Tier are getting stuck in the 'Queued' state, it's possible that a large number of concurrent runs were initiated in a way that violates the limits that have been enacted on your Domino deployment. You can confirm that this is the case by checking the Dispatcher logs for errors like the following:
2021-06-07 12:07:36,581 level=INFO [DispatcherActionProcessor]
Dispatcher: Action SkipQueuedRunExceedingPerUserLimit processed in
0ms correlationId="HTRKQN3DvJ" thread="application-akka.actor.default-dispatcher-183"
For more information on troubleshooting the dispatcher, see Dispatcher Troubleshooting.
Once it is confirmed that this error is present in the logs, there are basically two options: 1) tell the user that they're using too many concurrent runs, or 2) you can increase the limit of runs per user with the configurable setting in Central Config called:
If you have any further questions, please contact Domino Support at firstname.lastname@example.org.