Psyonix announced that they will no longer support the Mac and Linux versions of Rocket League, since combined they are less than a percent of the user base.
The last patch for them will be live in March and after that Mac and Linux users will not be able to play online matches or enter the in-game store. Local matches and splitscreen will still be available since they are not online features.
Devin Connors, Psyonix community chief, explained in a Rocket League subreddit post that Psyonix simply can’t justify the time and money required to keep the game running on Mac and Linux after the Windows version is updated to 64bit and DirectX 11.
"There are multiple reasons for this change, but the primary one is that there are new types of content and features we'd like to develop, but cannot support on DirectX 9. This means when we fully release DX11 on Windows, we'll no longer support DX9 as it will be incompatible with future content," Connors explained, "The number of active players on macOS and Linux combined represents less than 0.3 percent of our active player base. Given that, we cannot justify the additional and ongoing investment in developing native clients for those platforms, especially when viable workarounds exist like Bootcamp or Wine to keep those users playing."
To be fair to their Mac and Linux users, Psyonix is working with Valve to allow them to get a refund for Rocket League. It wasn’t working previously, but it should be working fine now.
Epic Game bought Psyonix back in May 2019, there are still no announcements concerning plans and Rocket League is still not available on the Epic Games Store, it’s possible we’ll only see it after the DirectX11 update.