Re: Ariston Advantage AS100
This is an Indesit made machine, the standard Indesit door latch is rather weak and often breaks but your machine does not appear to use the common door latch.
If you are very lucky the latch mechanism may just have flipped closed, this can sometimes happen even when the door is open. If it has you can usually see the latch in the wrong position through the slot in the door, in most cases it is possible to prise the latch back into place with a couple of thin screwdrivers or similar. Be sure to remove the mains plug first just in case.
If the door latch has broken then it will need replacing with a new one.