Assets used in a group game have to be uploaded to the group and not your account itself. Can either reupload or just give your game permission to use it
I re read your post and it says model so I’m assuming you’re using InsertService? I’m not familiar with it but it doesn’t seem like using the models cross group is possible? If the game is created by a user as long as they own a copy of the model it can be inserted. For groups it has to be uploaded to that group to be accessible
Roblox is just very weird when it comes to permissions like this