Are you getting a firewall prompt? Try running play-offline.bat and see if that works
I did try playing it offline, but it still shows a black screen.
(Edit: It might just be a problem with my pc)
Update:
I tried this on a different computer and it worked.
Could you try this for me on your original computer?
Go to C:\Users\{Your Username}\AppData\LocalLow\Mellow\ and delete the DriftKing folder and then run the game again, give it a few seconds after starting up to reinitialise the folder
If this works I’ll release a patch shortly