Please refer to the following solutions:
(1) Try to pop the keycap off and shoot some air in and around the cap first. Maybe it is just a dust/debris-caused issue.
(2) If it doesn't help, try to factory reset your keyboard by holding fn/fn1+ Z + J for 4 seconds.
(3) If your keyboard is hot-swappable, please change the defective key switch to a working one (you can replace the switch with one that works on your keyboard). There may be something wrong with the switch.
(4) If your KB is not swappable, it might be a switch problem. Gateron switches on your keyboard are soldered. If you are interested and have confidence in changing switches by soldering, you can contact us at support@keychron.com to get some switch replacements. Here is a video about soldering you can refer to: https://www.youtube.com/watch?v=RA2OHv3bEF8#action=share
(5) If you have a K series or C series keyboard, you can also test the defective keys here and shoot a video of the defective keys without keycaps on. If you have a QMK keyboard, please refer to this link to test the key, then contact us at support@keychron.com so our tech team can check it out and try our best to help you with your problem.