Microsoft.Dynamics.Service.Plugins Calling User is Disabled

Hi all,

When trying to create a new Case, I am receiving the following error:

• The user with SystemUserId=xxxx in OrganizationContext=xxxx is disabled.
• The plugin causing the error is 'Microsoft.Dynamics.Service.Plugins.PostOperationIncidentCreateEntitlement'.

So we have disabled that user, but from where I can control the calling user for Microsoft.Dynamics.Service.Plugins.PostOperationIncidentCreateEntitlement.
When trying to browse list of assemblies from Plugin Registration Tool, I cannot find Microsoft.Dynamics.Service.Plugins there.

I need to know how to change the calling user or team for Microsoft.Dynamics.Service.Plugins to fix the problem.