When setting up jobs in Project 2010 such as the Active Directory (AD) group syncronisation, these jobs get queued and then processed by using the Microsoft Project Server Queue Service, if you notice jobs are not completing or are in progress, confirm the service is running, if it is running restart it.
Restart the Microsoft Office Project Server Queue Service. To do this, follow these steps:
- From the server that is hosting Microsoft Office Project Server 2010, click Start, and then click Run.
- In the Run dialog box that appears, type “services.msc” without the quotation marks and then click OK.
- In the Services window, right-click Microsoft Project Server Queue Service and then click Stop. After the service has stopped, right-click it again and then click Start.
The article mentions Project Server 2007 but also relates to Project 2010 and 2013 http://support.microsoft.com/kb/2000241
Once started review the event logs for further errors.
likley causes for the service failing is communications problems to AD, SMTP failing, currupt jobs