Hey, I'm really sorry you have this issue. Did you try with both your keyboard and a controller? If yes, what kind of controller? Which build did you download? Did you try to rebind your controls?
A chest cost a key and shop items some coins make sure you have some (might sound silly, sorry but I have to precise it) by default you can open the chest with E or right bumper on controller. If you're able to take free guns on the floor, chest and shop gun should be okay too.