I hope this will help… I use a Pi4, went through days of different issues. The issue closes to your that I’ve experienced is not connecting to internet, so I obviously just direct wired it to my router. Then I tried to access my roms folder with my pc. I connected my pc to wifi , to the same network as the Pi4. I opened any window on pc and clicked on the location tab and typed in the following, //batocera.
It would then direct me to a folder named Share, I would try to open it and it would say I don’t have permission to access the folder named share.
I then went on the pi4 turned on a Batocera image I have. While on Batocera I went into System Settings -> Security -> then I turned off the Enforce Security option.
That helped me out, I know your using as pc and all you have to do is plug the pc, with Batocera on it, directly to your router if you don’t have a wifi doggie.
CHEERS