We have this exact senario.
Nodes show with a grey square
Node is Up.
Overall Hardware Status (Node) 'Overall Hardware Status' has state: Could Not Poll.
We found this article as the fix...all of our nodes pass said test with no issues.
I have tried force refresh of resources from the list resources menu
I have tried Edit node and testing SMTP
I have tried to uncheck the health status inside list resources and rechecking it.
Not sure why this happens, and not all of our nodes have it.
Every switch in each class is running the same firmware, some are working, some are not.
Any thoughts?