I just installed the 4.8 Version of unreal and tried recompile it with VS 2013 and I get the above error :
“Unable to start program: ‘C\Program Files\Epic Games\4.8\Engine\Intermediate\Build\Unused\Project_name.exe’'”
The system cannot fint the file specified.
I did what I think was enough to put the project up to date, going to the .uproject, right click on it and go for “Switch Unreal version” > 4.8 And "Generate Visual studio projects files.
On the other hand I’m perfectly able to launch the game via the Epic Games app / hub
I had a slightly different variation on this, wanted to post it in case it saves anybody time. dumb i missed it for so long.
Somehow my GAME project became deselected as the startup project ,and the UE4 engine project because selected. This apparently does not work at all. I had to re-set my game project as startup project
(Right click it in solution explorer->Set Startup Project)