help

I just bought a Yunzii b75 pro used and it just don't work. It's unresponsive to switching modes, when i plug it into my computer through the cable caps lock is stuck on and it's uncontrollable and spams random keys. I've tried 50 million different "FN + ESC" type combos but it doesn't change anything. The RGB is running and the space bar is blinking red. I'm pretty sure whatever is wrong with it is unfixable but I just want to make sure before I go return it.