OS: Windows 10 x64
Graphics card : HD7850
Radeon Software Adrenalin Edition 18.7.1

ZDL 3.2.2.2
GZDoom v3.4.1

All enemies and ammo are invisible .

It would be very difficult to play that way. But I'm sure I could do it for at least the first couple levels just going on muscle memory. I might have to put myself into an opium trance first, though.

Doesn't that kill the point of the monsters that are already invisible?

I just tested GZDoom 3.4.1 under W7 with nVidia 1050Ti card and all enemies & ammo are visible in all games (Doom 1-2, Heretic & Hexen). Suggestions:-

1. Go through the render settings in-game and see if something's changed?

2. Disable driver-level anti-aliasing on AMD Radeon drivers and use only in-game AA instead (Options -> Display -> OpenGL Renderer -> Multisample). On my previous AMD 7xxx series card, issues such as invisible trees in Age of Mythology or invisible cloaks in NWN were all down to AMD's driver-level multi-sampling. Either disabling it or using something else like SMAA / FXAA fixes it for a lot of games.

Fixed it . Used AMD Clean Uninstall Utility and let Windows 10 to download the driver .

And about as much fun as castrating yourself by slamming your balls in a drawer.