A pane that is not securely retained can make the door unsafe to use. Do not continue heating while its position or retaining parts are uncertain.
What the observation means
Glass layers, spacers and clips can have a prescribed arrangement. Reversing a pane or omitting a small part may not be obvious from the outside. The relevant event is whether the door was dismantled and how it was reassembled.
A useful next step
Leave it cool and unused, retain any removed parts and obtain model-specific help. Do not wedge the pane with cardboard or silicone. The appliance should not be operated with glass missing simply because the outer door still closes.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.