There might be multiple scenarios.
1. QV server service account might not have access to the source like DB/Share path e.t.c
2. The user running QMC task might not have access
3. In section access include service accounts,Account of user running QMC task.
Verify if you have service account added in QMC.
Check your db/file, if the views/table are altered and the extract file is not updated
