Symptom: Error message indicating that the following DLLs are missing: x3daudio1_7.dll / xinput1_3.dll or xapofx1_5.dll.

"The program cannot start because x3daudio1_7.dll / xinput1_3.dll or xapofx1_5.dll is missing from your computer. Try reinstalling the program to solve this problem."

Cause: DirectX DLLs are normally installed on your hardware with the installation program. Sometimes there may be a problem.

Solution 1 : Run “Prerequist” again via the file: UE4PrereqSetup_x64.exe

Located here: C:\Program Files\TOPSOLID\TopSolid Virtual 7.1X\Engine\Extras\Redist\en-us

Solution 2 : If this does not work, manually install DirectX: https://www.microsoft.com/en-us/download/details.aspx?id=35