How do you go fullscreen using the SRB2 Launcher without getting an error?

Whenever I use the SRB2 Launcher to play fullscreen, I get a message saying this: "Function call not supported"

Can anyone help me on this? I want to use the Metson and Metalknux wads, as well as SRB2JTE. Is there something wrong?
(I downloaded the launcher from SRB2.org, FYI)

Also, I'm using the current version of SRB2.

This also happens using the normal launcher (srb2win).

The crash is probably caused by SRB2JTE since it's not compatible with the current version. Try it with the official EXE. You can also get full screen permanently by entering "fullscreen 1" in the console.

Or if necessary, create a file called "autoexec.cfg" and type "fullscreen 1" in it.

If you're using JTE for bot support, try SRB2Cineblast < clicky
And don't use pre-2.0 character WADS (at least without proper editiation) in 2.0.6 and equivalent exes.