Absolutely the best server manager for AC, hands down (and I have tried them all in my time as a league admin). Trivial to install, immensely powerful and easy to use, for everything from quick one off races to complete championships with fully configurable race weekends.
The devs are responsive, both here, on GitHub and in their Discord. Bugs are fixed promptly, new features are being constantly added, and they are open to merging code features from contributors (I wrote the Discord integration, which they were very encouraging and helpful with).
Please ignore any 1 star ratings from people who couldn't install or run it. If you can read a short paragraph of instructions, you can run this.
This problem should be fixed by uploading the tracks on the Content -> Tracks page. We include enough stuff for the tracks to work by default, but we don't ship the images etc. from the game with the Manager.
Thanks!