In this particular case, this issue happened when a client task job, containing a quick delivery task, was scheduled against an endpoint that was booted up into automation waiting for a job to be assigned. In addition, when trying to schedule the client task job against the endpoint from the client job, Manage > Jobs and Tasks, the endpoint is quickly added and removed. Reviewing the SMP log files may reveal the following message: Removed one computer based on filter collections
Total license count exceeded. In addition too many computers were imported causing resource membership updates to fail.
In this particular case computers were imported into the SMP server through active directory import from the root level OU. This imported approximately 55,000 endpoints. This exceeded the total license count on the server. In order to resolve we were able to remove the majority of computers by selecting a large amount, right clicking, and choosing Delete.
If in a hierarchy environment you should not run active directory computer imports on parent level servers. Please review the following article: AD Import in a Hierarchy