If you're having trouble picking up items in Fortnite, it could be due to a number of factors. Here are a few things to check if you're unable to pick up anything in the game:
1. Make sure that your inventory is not full. If your inventory is full, you won't be able to pick up any more items until you free some space. To do this, simply use or discard some of the items in your inventory.
2. Ensure that the item you're trying to pick up is actually interactable. Some objects in the game world cannot be interacted with and therefore cannot be picked up (e.g., trees, rocks, etc.). Only attempt to pick up objects that have a glowing outline - these are the only ones that can be picked up.
3. If you're still having trouble picking up items, try restarting the game or your console/PC. This will often fix any glitches that may be causing the issue.