Can't login to WD ShareSpace from OSX, but can from Windows machine

I have the following issue from my (old) 4Tb WD ShareSpace NAS: when I try to acces this machine from any of the 2 iMacs in my LAN, I can see the drive, I get the login screen, but it fails to connect. It does not give an error message, but the login screen just returns…
When I login from a Windows10 machine in the same LAN, everything works as it should. When I run the setup program of the WD ShareSpace from the Windows machine, I can verify the I use the right user id/password.
I do not understand why I can’t acces the NAS anymore from the iMacs.
WD ShareSpace is on the latest firmware, iMACS are on latest OSX (Big Sur).
Perhaps it is time to replace this NAS, but I would rather understand what is happening.
Does this sound familiar to anyone?
Thanks!

Hereby the outcome, for future users with the same issue. In short, WD stopped the sport of the WD ShareSpace in 2012 - no firmware updates were released since then. As OSX has moved on, the WD ShareSpace can not be accessed from OSX anymore. No solution possible.
You cab however still access the NAS with a Windows10 machine - I would recommend everyone to move all data from the WD ShareSpace a.s.a.p. this way, before this is also no longer possible.