Hiya,
Unplug the appliance and take off the bulged cover on the rear.
This will expose the element and thermostats.
If there is a hole in the rear of one of the thermostats, use a pin to gently reset it.
If there is no hole, you'll need to test the thermostats to see if they are open circuit. (You'll need access to a multimeter and be able to use it to test them).
If they are open circuit, replace both of them.
Hope this helps
Let me know how it goes or if you need more help.
Thanks
Home Appliance Technician
Whitegoods engineer working for a multibranded national company in the UK.