OK, in the top of the oven is a cooling fan. This runs to keep the electronics and controls cool, when the oven is running.
If the fan fails there is a thermostat which cuts the oven off totally, so as to protect the electronics
This is what is happening here
You will need to check the fan itself, as this is the most likely culprit.
If the fan has failed, you will need to replace it
If you need more help, please just ask.
In the meantime,
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