Hello Ricardo, did you maybe had a spill onto the keyboard?, also if the unit is old, ( i don’t know how old) some buttons might stop working , like buttons of tv remotes, it might be worth it to open the whole thing to have a look if its dirty or worn out . if its worn out, there is a conductive glue available from specialised electronic shops, just cover the tip of the missing carbon rubber with a very thin layer of the conductive glue , wait for it to dry, reassemble. also while you have it open, maybe then you can check if bridging corresponding pad of the reset option would do anything. good luck.