Normally I'd expect flat non-textured images as a result of having pressed the F5 key which turns off the lighting.
Here's a quick thought to start with:
Start up ArtRage while holding down the spacebar to delete the Artrage settings file and return it to default settings. You will be able to tell you've done this if Artrage pops up the update check as it launches.
Then, draw a stroke of paint on the canvas. Check that you see bristlemarks as expected.
Once you've verified this, go to the File menu -> Export as Image -> Choose the filename and format and save and check your result.
Let me know how you get on, I look forward to solving it!