I have added nodes in NPM and they are showing up fine. I can even view nodes in NCM Summary and view past versions of configurations. However when I go into Configuration Management to see the nodes and set baselines, it just shows a blank screen.
There's this link which seems to report an issue with ambiguous custom properties but I've checked the same log file and can't find anything similar:
Nodes missing from the NCM Configuration Management View - SolarWinds Worldwide, LLC. Help and Support