I've seen this issue a few times over the past year where I've received an email from a teammate saying "Hey Joe, we didn't get any disk space or CPU alerts about "Server X" last night when we should have. How come?" When I check the server stats in the SolarWinds dashboard everything looks good. But when I try to List Resources, the "Wait" indicator just goes on forever.
In trying to make the polling work, I've switched the polling type from SNMP to WMI, and vice versa -- deleting all historical data when making the switch -- and it still wouldn't work. The only way for me to resolve this issue is to completely delete the server, then manually re-add it again. Only then will SolarWinds properly poll the server and start gathering statistics again which also starts alerting too.
With monitoring over a thousand servers I've only had to do this twice so this appears to be a rare issue around here. Just wanted to share my experience in case others had the same problem.
