Jac m wrote

What is this red sign

Its saying that it will explode in one hour and 3 mins.

and how do I get it off

Use the largest hammer you can find or an angle grinder.

as the microwave is not heating now

Thats because it is saving the energy to explode with.

https://www.homeownershub.com/img/kq

Might help if you listed the model number or had a
photo of the metal plate near where the cord goes in.