Items do not want to appear in my bag. What could be the problem?
If you are trying to pick up dropped items then first make sure the item works if you placed it in the scene manually. if it works there then go on to using its prefab in the loot system.
Have a look at the docs describing how to set up items and loot tables if you have not yet
There are also videos describing how to create items https://www.youtube.com/playlist?list=PLuaBtUXEKcdJCbNoDg0tJ9TUdkNRDrKlI
Can you see the item on the floor after it was spawned? If not, look in the hierarchy to find the object and select it so you can see where it is in the scene view. Pause the game with Unity pause button while doing these things.