Everything is under the First person character at least but AssultRifle is not under Items ORG-hand_R but instead under the other Item folder.
I will delete everything and start over again, the problem is I follow the tutorial videos but somehow it doesn't work for me.
Started a new scene and now I have the same problem I can't build the item.
Maybe something is wrong with my installation.
Because I installed the assets Third person and First person separately I was told that was the same as Ultimate controller.
But I can't add UI setup and Virtual Controls setup so maybe it's more stuff that's wrong.
I can't even add one weapon. I was going to add 10+ weapons and that just feels impossible if I can't even add one by following simple guides.
Later I will try and install just Third person OR First person asset, not both and see if it works.
My previous message is correct only for the first item.
But if you create not the first but the second or next weapon, you shoul assign "base" and "right hand" from marked object on the screenshot.
You shouldnt instantiate a new "first person arms" in this case.
The guide above is really good showing what references need to go where. I recommend double checking that part. If you also go through the item creation video it'll show this visually.