I had the same issue, so when I updated my version of Unreal Engine, it worked. Doesn’t have to be with the latest version, but that might help if this way doesn’t
- Go to your Epic Game Launcher App
- Go to your Library from the Unreal Engine tab on the right-hand side column
Unreal Engine tab > Library > Engine Versions - Update your version, check which version the game/ plugin/ marketplace DLC is accepting
- Once it’s done, it should go from Unavailable to Download and should work now