Hey! I'll gladly help.
There are 2 ways to solve this puzzle. Easy one: QR code on the same floor contains solution. Hard one: look for the small square holes on the floor located in some rooms on this floor. They are hints for the right combination. If you can't progress any further buy a key from the merchant or look for the key you might've missed on the previous floor.
Anyway if this comment won't help you let me know. I'll give you a solution.