the key is just a big jumper pin, heck if you insert the key w/ batteries in, you'll see a spark, lulz i did.
but are you saying, the two middle leds flash, basically led 2 and led 3?
i've researched and that means it overheated
1. was the mower left out in the sun and it heated up?
2. was the deck low or high?, you said it was your first mow of the year, so the deck should be high.
3. have you checked your mower blades? this is how you can tell if your blades need to be sharpened
i have upgraded my mower to the same crosscut blades you have and it is really night and day in the cut speed, however you want to make sure your blades are sharp to ensure youre not taxing the motor too much.
the ryobi blades are light and soft(metal) and easy to sharpen, i can't tell you when to sharpen your blades cuz i have ocd and i sharpen em everytime i take out the mower.
Had the deck high, I checked the blades a tiny bit and they didn’t seem stuck, checked the small bit of grass that did get cut, and it looks pretty clean. Mower’s been stored in the garage this whole time and yesterday was only 60 degrees, so I can’t imagine it overheating in that. And yes, LED two and three.