P45 Yamaha digital piano keys stuck

the 5 central keys of my P-45 Yamaha digital piano are stuck, even though the sound works. I tried to clean it but nothing changed. I can’t afford the technician so I need to find a DIY solution; do I have to replace the keys even if the sound works and/or is a possible humidity problem? I moved recently so it can be also the cause of it. Thank you for your help !