Pi3 won't boot up (Green light flashes four times)

Hey there!

I got the Picade for Christmas and I set it up. Now I have two problems. First, I had a constant red light, but no green. So the pi didn’t boot up. I bought a new SD card and set it up. This one works fine! So I played with the arcade machine and even restarted it a few times. This morning, when I wanted to turn the pi back on, nothing happened again. Now I have the red light and the green light always flashes four times. I formatted the SD card and reinstalled Retropi. Without success. I even tried the old SD card. Now I have exactly the same problem there.

I really have no idea what the problem is or what I could try. Do you have any ideas?

Have a look see here,
I had the 4 green flashes on my Pi 4B and it turned out to be a bad SD Card.