NAS not allowing additional users?

Running Big Sur on iMac with Buffalo LinkStation LS210 network attached storage (NAS) for my home. This NAS has always been troublesome about staying active on the network. Recent outages meant I had to restart it, and reconnect it to the network, but Finder did not automatically mount it. I used Finder Connect to Server but no NAS device found on the network. Used IP Scanner app to scan network: IP Scanner finds and pings the NAS, and reports the IP address. I used the IP address in Connect to Server to map the NAS. When trying to map using https:// Finder says "This file server will not allow any additional users to log in." When trying to map using smb:// Finder says "The server may not exist or it is unavailable at this time." This exact problem is in Apple Support for an older OS, and the comments say that OS changes have affected the process but give no details. Suspect there is a plist or some such file which can be deleted to allow the NAS a fresh start, but I cannot find any info about which file that might be.