When the watchdog service just isn't able to poll the servers, it's usually because:
- Either the community string doesn't match.
- There is an SNMP connection failure somewhere
- The SNMP service is not running on the target server.
To check the community string used by the watchdog, click on NFA administration at the top, then Watchdog settings on the left. Make sure the community string being shown is correct.
Then go into windows services and check the SNMP service properties on each server, and make sure the string listed on the security tab is the same one as the watchdog. Also make sure that it is set to accept from any host, or if you prefer to define the hosts, that the IP of the NFA master console server is present there.
Once all that has been verified, try restarting the Watchdog service on the NFA master console server. That will force a repoll of the components. Then refresh the system status page, and see if the errors clear.