Hey there @4Dface! Welcome back to the community! Depending on the issue at hand, there’s many possible solutions. First we need to figure out what’s going on.
Did the project crash upon trying to load? If so, may we have the crash logs?
If it just stalled during the launch process, what percentage did it stop? How long did you wait if it was shaders?
If you set a different starting map in your DefaultEngine.ini file (located in your config directory of your project), does it launch?
[/Script/EngineSettings.GameMapsSettings]
EditorStartupMap=/Game/ThirdPerson/Maps/ThirdPersonMap.ThirdPersonMap