DIAGNOSIS Two main causes. Most common: water remains in the drum or drain system. Less common: a failed door lock actuator (the latch mechanism).
FIX First, run a Drain & Spin cycle. This will pump out any residual water. Wait for the cycle to complete fully. The door should then unlock.
IF THAT DIDN'T WORK Unplug the washer for 5 minutes. This forces a hard reset of the control board and the door lock mechanism. Plug it back in. The door should release.
HEADS UP Never force the door open. You can damage the door handle, lock, or the glass. If release tab is accessible (check ), use it only after confirming no water is inside.