Expose the pressure switch at the top of the washing machine by removing lid, when the door wont open remove the pressure tube from the switch, if theres any blocked air this will release and activate the air pressure switch.
Find the rast connector which feeds power down to the door interlock, test at the connector block on the pcb for 230 volts, if 230 is present then its either a peripheral device or the pcb which wont allow the door to unlock.
On some door interlocks there is also a pressure pipe which feeds to a moulding on the drum, again this would stop the door from opening