F5 BIG-IP Devices appear grey in SCOM

If F5 BIG-IP Devices appear grey in SCOM here are steps what needs to be checked and done:

Go to Monitoring pane -> Active Alerts and check if there is warning – Network Device is Not Responding.
If there is, then, right click on that warning and chose Open -> Health Explorer -> click on SNMP Ping and then Reset Heath
Wait for couple of minutes for monitoring to start again. 

In case that this suggestion does not help, navigate to Monitoring pane -> Management Server -> Management Servers State. 
Click on management server on which you have F5 BIG-IP devices and run the Heath Service Task Flush Heath Service State and Cache.
This alert usually indicates some kind of issue with communication between the management servers and the BIG-IP device. This is a default SCOM functionality, but since we are leaning on SCOM Networking Management Pack it is affecting our workflows as well. It is possible that this is happening because of several reasons:

• The community string or SNMP allow list was changed so the management server doesn’t have enough access to perform an SNMP query on the BIG-IP device
• There is a high latency when BIG-IP device is responding to the SNMP query

If the device is running without any issues it is possible that we tune these monitors to compensate for the potential latency in BIG-IP response. That can be done by overriding the ICMP Ping and SNMP Ping monitors:

The final step would be to disable these monitors, but we wouldn’t recommend this before identifying the exact root cause for the alert being created in the first place.