If renaming it .mpg or .mpeg & you should try both doesn't work then Try Super it's a freeware converter.
You should also get a file checker like GSpot freeware also.
Then at least for the first conversion match the information it gives you to the settings you make in Super.
On Super sometimes you need to try both the MEncoder & the ffmpeg sometime one works better than the other depending on the specific file.
Then see if the converted file will upload.
@Kerry56 ;I haven't tried Vob2mpg but if you suggested it it's probably a good software.I'm not very satisfied with MediaCoder after some testing so I'm not recommending it.