The key has broken or snapped inside the lock because the inside mechanism is faulty or the key is not spinning at its should be.
There should be a question mark if the key it\’s a bit stiff when is turned. That’s not a good sign. Call a locksmith asap. This minor stiff could end up in a terrible lock out.
Wood door , composite door, upvc door doesn’t matter, of course the door locks with blocked hooks and gear box jammed are the worst case scenario. Every blocked door is difficult. No one is servicing the door and as time flies the mechanism will be adding shrapnel, dust, rust, loose pins, loose levers and it will affect the lock or mechanism wich will lead to a stiff key, hard to turn or even impossible to turn the key.
So save the time and effort call a locksmith.
Avoid being locked out or a locked door.