It shows se and will not work

You have blown a fuse. Check inside the oven chamber and look for missing powder paint or signs of arcing, if so there is a paint to repair microwaves for this issue or else just dispose of the microwave. If the inside is good remove all the screws and remove the cover. Replace the fuse. If the magnetron was making louder noises prior then replace the magnetron. Since the fuse went the giant capacitor is likely bad. While the cabinet is open make sure to look for burned wires, check the continuity of thermal cutoffs, and check the main circuit-board for burned traces or components. The relays in most electronics are known for arcing (spot welding) and staying in the wrong position. Tap them hard with the back end of a screwdriver. During all of this use safe electrical practices by having the power cord unplugged. The capacitor could still have a high charge on it so be careful.