Item pick-up issues

Xbox One X user. Had a couple of item pick up issues. 1. Were unable to pick up Meseta near a blue rarity rifle. Made the inventory full sound even though no items were being selected. 2. Unable to pick up some skills. Acted like inventory was full when it wasn't. Both times were from boss drops on the urgent quest.

Same situation. I have few items and can't even retrieve or pick item. Not sure what is missing. I was reading that there are 50 slots, how to find out how many slots are available ?

if you are using a keyboard just press i, it will open your inventory and there you can look how many slots are being used