Hello, I bought a keystep yesterday. After unpacking, I checked and played the keyboard, everything was fine, and all the keys were working properly. But today, when I turned on the keyboard, the Ab1, E2, C3, Ab3 keys did not work. When you press on them, the midi message is not sent, and there is no sound. I installed the software and updated it. I disconnected and connected the cable, but nothing helped. All other keys and controls are working properly. Everything would be understandable if these 4 keys did not work initially, but the mystery is that yesterday all the keys worked fine. Instruments preferences reset didn't help. What could be the problem?