Question regarding authentication between FreeNas 11.3-U5 and Windows 10 File Explorer

[kaz1946]

I am currently running FreeNas 11.3-U5 and Windows 10 Version 20H2 (Build 19042.868). I have been using FreeNas for at least 8 years on a network with 4 Windows 10 systems without any issues around authentication. I believe that I started with FreeNas 9.X - can't remember the exact release. In any event, with upgrades/updates, both in Windows 10 and FreeNas, I started seeing authentication issues/challenges appearing. I used to have a relatively issues-less environment for the longest time. Now, these weird authentication demands started to appear - making my anxiety increase. I have been using the FreeNas server as a file server, only. It gave me what I wanted - backup system for my files and MP4 storage for my movies. I am by no means steeped in security, for the entire network is on my LAN, which I think is pretty well protected from prying eyes. So recently, Windows' File explorer would cause an authentication window to appear when I clicked on the FreeNas icon appearing in the Network section (left panel). I have one group defined in FreeNas with 3 users defined and in that group. I guessed that in order to satisfy the authentication request, I could choose any one of the 3 users' ID and password to satisfy the authentication challenge - I tried all three user IDs/passwords with failure. So, in a last attempt, I used the Root Id and its password and voila - it worked! I would like to understand how using the Root ID & password to satisfy the File Explorer challenge - I know that I'm missing something. Someone, please help me understand.