[2020] Navezgane is the only playable map

I mean... The other maps are fully playable even without traders. Traders are not necessity in the sligthtest; Just nice to have.

That said, I'm unsure why you're experiencing the no trader issue.

No traders means it is an A18 map, pure and simple.

Start the game and choose: Show game launcher
Select the tools tab in the launcher window
Select Clean game data
Check every box and then select clean

Close the launcher and then start the game for real.
Start a new game and try one of the pregen maps
DO NOT NAME YOUR GAME THE SAME NAME YOU DID IN THE PAST

Hopefully you will have a trader this time.