Washer door won’t openSome door locks are time delayed so make sure you have waiting a couple of minutes before proceeding. Most washers will detect when there is still water in the machine and prevent the door opening. Check also that that isn’t the case (see Washing machine won’t empty)
You will then have to check interlock itself. Depending on the model, access to it can either be from underneath by lying the washer on its side, or by removing the top cover and putting your hand down the front. Make sure the appliance is unplugged before doing this as there are bare wires around that area that could electrocute you.
The interlock is behind the hole where the door catch enter the main case. Sometimes the lock is controlled mechanically and there is a cable connected to it which can be pulled and disengaged.