Retropei won't boot properly after picade x hat installation

I have a Picade X-Hat connected to Raspberry Pi 4B, in a self built arcade machine.
I followed the instructions in Assembling your 8" or 10" Picade with PICO-8 and and ran the Picade Hat installer. When rebooting, I don’t get the Retropie logo screen, but instead a rectangle with blurry colors, followed by the reboot messages (all with OK label), and ending in entirely black screen, from which I can only get to the console by F4.
This is the second machine I am building, and I think I had this issue also in the first one, but I cannot recall how I solved it.
I would highly appreciate any help.
Best regards,

I have the same problem… Total noob… anyone help?