when you say "DEP screen isnt popping up" are you meaning DEPNotify and not the Apple setup assistant window "Remote management"?
A few things to look at:
• Have you re-uploaded or changed the depnotify.pkg file? if so is the signed certificate applied to the pkg?
• does this happen for automated enrollments or some sort of other enrollment such user initiated?
• is it properly scoped to All Computers and not scope to just certain devices (ie; High Sierra, Mojave)
• are you using the StartDEPNotify script as well?
This is for a prestage enrollment. The Remote Management screen does pops up. When the user logs in after enrolling a new machine, the DEP processes kicks off (enrollment complete trigger) and then the rest of the policies in the array kick off. The problem is, the DEPnotify window that displays what's happening in the background isn't showing up at all.
I have it scoped to "Enrolled via Automated Device Enrollment". I am using an older depnotify package (1.1.0) but I'm unsure if adding an updated package would affect the script I have at all.