Where is this information found on the web-interface? I am running Observium 0.15.2.6240.
I did find a temporary work-around to get this information:
1) Perform a debug discovery and save the output to a file > "output.log"
2) Search that log for "autodiscovery fails".
grep "autodiscovery fails" output.log
This will give you the hostnames of the devices that failed discovery, perhaps because:
"Host AVX5BE9F3 not resolved, autodiscovery fails."
Actually, this will not help in many cases when the admin doesn't know the IP of that hostname. Observium needs to tell admins the "Management IP" that was gathered from xDP.
Fixed in recent (rolling) versions.