Symptom
AV Defender shows Days since last successful scan has exceeded the set threshold (see example below).
Resolution
1). Log onto client computer
2). Navigate to 'C:\Program FIles (x86)\N-able Technologies\Tools\AVDefenderEvents'
3). Delete the file(s) '6000_SCAN_*.xml'
Conclusion
After applying the resolution N-Central will poll the client computer and the error will no longer be presented.