You can't watch DVDs from other region because they have a different encoding. For example, Europe uses PAL, USA/Japan uses NTSC-U/J. Most likely the software you use doesn't have support for the format of the DVD you are trying to play. I recommend converting them. It can be a tedious process at first, but at least you will get functionality.
To do this, install DVDFab and convert the DVDs to a standard AVI or MKV file then burn the files back to a DVD in standard format and according to your region and they should be compatible with your players/devices.