Found one of many possible fixes.

If you and your friend are playing between the Steam version and the gamepass version, game pass is NOT the latest version of the game, send the steam versions files to your friend and have them copy them in the mod directory as per the instructions.

Steam stores the files in your \steamapps\workshop\content\976730\2962107814

Copy the folder named 2962107814, zip it and send it to them.

Don't ask me how to fix your game if this doesn't work, I can't help you further.

Have fun.