Though not entirely the same configuration (it was a Pi 4), I encountered an issue wherein after the boot sequence the display would be completely blank. I eventually narrowed it down to the memory split setting - I had changed it, trying to follow the instructions for RetroPie 'manual installation.' Keeping it default resolved the problem.

Maybe a stupid question, but have you installed the HDMI adapter that connects the Raspberry HDMI to the HDMI of the Game Hat? You probably had to remove it to install the Raspberry to the Game Hat, but after doing so you need to put it back!

@Tephra If using Win32diskImager unzip as @quicksilver mentioned, or if using Etcher you can flash the image directly to the sd card.

it was working ok,
but yesterday i start soldering the cables from my pc controller pcb to my buttons ( to add the light to my button) while the Raspberry was on. Then after i finished i lost the screen.

Tried turning the RB on without controller but that din't make the difference.
I think its just broken, better get a ODROID-XU4 instead of a Raspberry now :-( .

Well finaly i got to putting om my new powerblock after putting in the script code it seemd like it went the same way as the previous version with the rebooting and all.

I removed the powerblock went in to the retropie setup and updated the installation script, then went to the drivers and installed the powerblock from there.

After a reboot it works like a charm now.

Thanks Florian

Retropie rocks !!

It was the SD card. Apparently nothing was loaded on it....

After imaging a new SD card the HDMI picture came back on my monitor and all is good in the world.

In case anyone has this problem and looks at this post in the future...

If you have no signal on your monitor theres no green flashing light (data read activity) next to the red light (power) on your RPi circuit board your SD card is bad - re-image another one and you will get your signal back on your monitor.

Equipment11bolded text
Alright i got it working. So it was the image file that was corrupt. I tried 2 more sd cards and it wudnt work so i redownloaded the inage file on my phone. Then transferred it to my computer and extracted it and tried again. Its now working. Thanks a bunch man