Storage....
With this thing sitting up for over a year, I'm going to assume it wasn't prepared for storage before you put it to sleep.
The 717 is a really good engine. There are so many things that can be wrong, I think I'd just start going over everything.
You know the mpem works, or you wouldn't have fire.
I'd say, it's most likely your carbs are either going to need to be cleaned or rebuilt.
The red light and siren.........I've never heard them with a siren before.
The advanced mode on the DESS......you can try.
With the lanyard cap off, press the start stop button 5 times. You shoul hear one long and one short beep. Then, put the cap on. When you put the cap on, if you hear any other beeps, count them. Re-post them in the forum. If you don't hear any additional beeps, then that is a good sign that the engine is ready to start, providing the fuel system, etc....are clean and ready to go..........