I had the same issue...now resolved. It was this missing Nvidia file: Vulkan-1.dll
i found a link here in the comments to download something, then located the file there, moved it into my main X4 file and presto!....it worked. Check if this is the issue by trying to start it directly from the x4 file...hit the icon in there and if it says "vulkan.dll file not found" or whatever, then you have your solution.