Here is what may cause your garage door opener to not power ON:
1 – The transformer has failed due to a power surge.
2 – The glass fuse on the circuit board has blown or popped.
3 – The circuit board itself is faulty.
4 – A wire or wire harness is loose or burnt.
5 – The end of the electrical cord has become disconnected from the opener terminals.
6 – The electrical cord itself is damaged.
7 – Bad capacitor.