Sorry for the delay in getting to your question.
Is this a free standing or integrated microwave?
Does the door drop down or open to the side?
Open the door.
You shouldn't see any screws.
The inner part of the door is pressed into place.
Use a flat blade and lever the inner part of the door out, go slowly and work round the door, levering out a little at a time.
Once you get the inner part out, you'll be able to change the latch assembly.
Check it out, see what you find and get back to me.
Hope this helps
I mean the inner door.
It's the larger part that fits into the larger part of the outer door.
Sorry, I can't explain it any more clearly, have a good look at the door and you'll see that one is pressed into the other.
I'll opt out of the question and open it to all again as I'm going offline now.
See if anyone can explain this in better terms.