I Cant Decomp Any File

[Viper939]

i get this error

[Viper939]

this happens every time

[rihi]

As far as I know this is an issue with third party gmad extractors. The file is missing its first byte.
You could try opening the map in a texteditor and add a 'V' at the beginning or alternativly extract the gma again, using the gmad.exe bundled with the game.

[MARK2580]

I've been using this gma unpacker for several years now and never had a problem. Try it. (you just need to drag gma to exe)
gmadconv.zip

[rihi]

Can you share the workshop link of the bsp you are trying to decompile. The gma unpacker does indeed seem to work for other bsps.