There are several different ways of securing the microwave in caravans , look for 'secret screws' sometimes underneath the shelf.
On a recent M/home The microwave was behind a hinged cover , identical to the adjacent cupboard door, on opening the door of the microwave there were two countersunk -secret ' screws securing the hinged cover shut, removing these allowed the cover to open allowing full access to the bracket which secured the microwave inplace -Very elegant I thought and that was on an Elddis.
PS the main failure of Microwaves is the phase angle correction capacitor for the magnetron, due to the lack of ventilation around the microwave sides and rear. Replacing it ( about a £10 off Ebay) usually gets the thing working again - Safety point - never, never ever run a microwave with covers removed you only get two eyeballs and microwaves can superheat them in seconds!