You can check the following using SQL (let me know if you need more guidance on this part), running it against the company database:
select * from UPR10200
If no one is actually running a payroll, or has a build in place (you can have users go to Transactions>>Payroll>>Build Checks, and if the Remove Build button is available...they have a build in progress); then there is a routine to run through to clear out the stuck activity. Let me know if you need it.
Take care,
Christina