Please follow the following steps to troubleshoot and handle the issue:
1) Turn the key to 90° and turn the handle;
2) The key is incorrect, replace the key;
3) The latch of the lock body is stuck, and the door is tightly against the door frame. Try turning the handle or using your hand to hit the lock tongue and the position of the door frame;
4) The lock cylinder is stuck, disassemble the lock for inspection.