First of all, a huge "thank you" to GOG for bringing back this gem from the late '90s. I enjoyed the Requiem demo back when it was released and I've been itching to play the full game!

Too bad that, now that I finally got to buy it, I can't even get to the main menu...

When I launch the game via the D3D executable, all I see is a black 640x480 screen and the system cursor. Clicking the mouse has no effect. Alt-Tabbing out of the game, I get a popup window saying: "ATTENTION! Network problem: Could not connect."
The same thing happens with the 3dfx exe, except I can't even Alt-Tab out of the game window. Pressing Esc closes the popup and brings me back to the desktop, but sometimes I can get a glimpse of the popup right before it closes.

I've tried Win9x or WinXP compatibility mode with no success. I get the same error popup with the D3D exe, but I don't have to Alt-Tab out of the game in order to see it; the 3dfx exe spawns a different popup indicating that the game can't detect the keyboard (?!).

Here are my PC's specs:
CPU: Intel Core i7-4702MQ 2.2 GHz
GPU: Nvidia GeForce GTX 850M + Intel HD4000
RAM: 8 GB
HDD: 1 TB
OS: Windows 8.1 64bit

Any ideas on how to solve or at least work around this issue?
If you need more details or I haven't been clear enough, I'll do my best to provide more complete info.

Thanks in advance!

Update
Tried running the game through D3DWindower, it keeps crashing.

Just for kicks, I also tried to run the game (3dfx executable) through Wine in an Antergos Linux VM. Sound doesn't work and there are graphical glitches (as expected), but the game is playable.

I have the same problem.

Environment:
Intel Core i7-4770K @3.50 GHz
32 GB RAM
nVidia GTX 770
Windows 8.1 64bit German

Same thing here as well.

The game starts with the 3DFX logo, followed by a black screen. ALT-tabbing reveals the error "Attention! Network problem: Could not connect.". Clicking OK on that dialog just closes the game and there's no way to proceed.

CPU: Intel Core i7 3820
RAM: 32 GB
GPU: Nvidia GTX 1060
Windows 10 64-bit (version 1703)

Can confirm I'm also suffering this issue on my gaming laptop, though on my desktop it works fine. I hope this get's resolved soon!

Worked for me. Thank you, you're awesome! :D

Confirming fix works, was almost going to refund this but it plays now.

Wow... I haven't checked out this forum in a while, and I'm surprised this thread hasn't been forgotten :D I can confirm the game is working. I'll mark your post as solution.

Thank you very much!

Totally works - thanks a lot, mate!