I have 2 screens connected on my Radeon HD 6770 and for a reason, when i exit the TTY and start Dwm one of them go black.
Figure out first if this is a dwm problem. Does it work in openbox (or whatever)? What does xrandr say?
Is it the same one every time or is it random? What DWM? Do the two screens use the same type of cable to connect to your GPU? Does power-cycling your black monitor or disconnecting/reconnecting the cable fix the issue?
It's always the same screen, and disconnecting/reconnecting dosn't work. im starting to think it's a screen issue
What happens if you swap which cable goes to which screen, or only have the black screen be connected?
It could still be a DE config issue since the config can identify screen ID based on some kind of ID given by the hardware (sway can do this for example). What DE are you using and what is the text file config related to screen output?
I'd start here: https://dwm.suckless.org/multi-monitor/