There is currently an issue with macOS 11 Big Sur where Active Directory users are not issued with a Kerberos Ticket-Granting Ticket (TGT) when they log in. As a result, you may see network shares managed by NoMAD failing to mount and other Kerberised services/websites prompting for username and password authentication.
NoMAD's menu bar icon will not have the usual green tick in the icon, and instead will show an empty black triangle:
To test for the issue, open Terminal and run the command:
If the issue is present, you will see output similar to this:
klist: Cache not found: API:D9911538-40E0-4E8C-9FE8-1859E027400C
The issue is caused by the user's pre-Windows 2000 logon name (sAMAccountName attribute) containing uppercase characters. Change this to use all-lowercase characters and Kerberos tickets will be issued at login as usual.
NoMAD's menu bar icon will also have a green tick: