The butterfly keyboard introduced in 2015 by Apple on the MacBook 12″ and then gradually generalized to other laptops will have made many fans of the brand see a lot.
Except that the butterfly keyboard quickly proved to be very sensitive to dust and debris. Much too sensitive! A particle that has the misfortune to get under a key and a key is blocked and won’t go in anymore.
Unlocking locked keys on a Mac keyboard
check that no crumbs or dust is stuck on the edges of the key, by inserting a sheet of paper all around the key:
Blow or use a pressurized air canister to remove dust: