In order to read a wide range of 360 video, CinematicVR Panner relies on video codecs available on your system. We strongly advise installing K-Lite codec pack. They are powerfull and we have been using it successfully on a lot of computers with various format, from mp4 to DNxHD.
To download it, go to official download page and get the “Standard” pack. On the next page, choose a mirror (for instance “Mirror 1”).
During install, you can keep default choices BUT beware that K-Lite installer will suggest installing additional software. You are perfectly free to decline.