m1000e's not being monitored correctly

Hi,

SCOM2012R2, Dell MP6, we get the following:

Where you can see that even for the same Management server, (11) one chassis is monitored OK and then another has an open circle.

Out of 47 chassis only 16 are in the fully monitored state. I have deleted the IPs of the chassis from Discovered Network Devices and re-discovered them but to no avail.

All the chassis are operating fine. Nothing in their logs to suggest an issue.

Can someone pls shed some light on what to do?

Thx,

John Bradshaw