I would be interested to see if this result is replicated in the Polling Engines page. I am not sure if hitting this page causes a live connection to the APE or if a value is returned from the database.
The Engines table has a column LastUpdate which you can query to see if it is doing its job. Also if you have SAM you can do a test to the 17777 / 17778 port as as HTTP / HTTPS monitor (in new version you would use the API monitor type, which we are very much looking forward too.
I'd suggest to restart Orion services and check again if NCM has issues. If yes - run Config Wizard. If will not help assign case to SolarWinds.