When you have a worklist hosted inside a SmartForm application, some users are not able to view their worklist items when a new task comes in. Only the Task originator is able to see this. The task is assigned to a user group via Active Directory. Executing the AD Group SmartObject you are able to see all the members of the group.
When trying to load up the worklist within the SmartForm application, this fails to load and an infinite spinner is shown.
Make sure that the domain group or the 'everyone' group is added under the security section via the environment library. This can be accessed through the management page. Giving the group modify and read rights should allow all users to have access to see their worklist tasks as expected.