Not upgraded yet but I assume you can list resources on existing nodes?
i am also on SQL 2016, what version of npm did you upgrade from?
I am having the same problem. After upgrading to version 12.2 (with HF 2) it is no longer able to list resources on a node. It just spins indefinitely and never shows that it found any resources. This happens for me both when I try to add a new node AND when I try to list resources on an existing node. SNMP is working and NPM is otherwise able to monitor the already monitored resources for the nodes without issue.
I upgraded to hf2 then about 20 of my agents broke it all looked ok but all the interfaces went unknown.
list resources didn’t work had to remove the agents and the folders on the clients and reinstall took from 10pm to 5 am to fix.
not 100% it was the easis fix I could of done but needed them working for 5am as it looks after are IIS restarts if they don’t work.
I ended up opening a support case with SolarWinds for this. After sending the engineer a diagnostics file he observed there were errors in the install log from the upgrade to 12.2 (I had upgraded from version 12.1). He had me rerun the configuration wizard and that cleared up the errors he saw in the install log, however did not fix the problem. Running an SNMPWALK against a node showed all of the resources for the node, but it would still hang when doing a "list resources" in the interface.
He then manually installed and reinstalled the various SolarWinds services one at a time, and opened the database manager and looked at several items and made a couple changes. After these changes we are finally able to list resources and add new nodes again!
Unfortunately we moved through those steps too quickly for me to make notes. I apologize I am unable to provide the exact fix for it here. If you are having this problem and end up opening a case hopefully you can get better notes to report back with than I did!