If a Windows 7 client does not have a WSD subscription and a WSD print job is sent while the printer is in a "User Intervention Required" state, the job will not complete until the device is powered down or the spooler is restarted.
This issue is due to the Windows 7 client not having a WSD subscription to the WSD printer. Some WSD devices have a subscription limit on active connections to the printer. When a client does not have a subscription to the printer (exceeded the number of available subscriptions for the printer), it will not receive notification that the printer has changed status from "User Intervention Required" to "Ready" causing the print job to remain in the print queue. If the printer power cycles, or the spooler is restarted, Windows will then recognize that the “User Intervention Required” condition has been cleared and the print job will process as expected. Windows clients that do have a subscription to the printer will recognize the change in status automatically.