I was using 7.0.1 in N40L, both Synology assistant and find.synology.com no problem finding the device.
But after Updated to 7.1Find.synology.com and Synology assistant cant find the NAS.
Device working fine, can find via IP address though.
Just sharing.
I have N40L too, successfully upgraded from 7.0.1 to 7.1 using Peter Suh instruction.
I don't install any other nic, using the built-in nic only.
No problem getting IP.