Rainbow screen after trying to setup 3.5 touchscreen

[vongdong]

Hi all,

Just got my first Raspberry Pi (4) and tried to install/setup a 3.5" touchscreen using this guide https://www.youtube.com/watch?v=ontgsOFEv88 but now am stuck with a rainbow screen on an external display. I followed the command to the last step then it decided to reboot itself and now stuck.

What can I do?

[vongdong]

I'm also using an external touch screen display through the hdmi and the touch doesn't even work on that. I updated the system at installation.