Ideally this happens for larger database , it is observed 24 hours report seems successful during our testing phase however 7 DAY or fortnight report is generally affected.
WORKAROUND
1. Try running the same report for last 1 day to see if it works
2. Server setting -> Reporting -> Stats collection Records per storage file -> increase the value to 32,000
STATUS
Enhancement request number (NV-I-739) has been submitted to Development for consideration in a future release of (Netvault).
