https://www.free-codecs.com/hevc_video_extension_download.htm
The latest version is 1.0.43421
You know you need it. The X64 one. I just installed it and it's working fine. For all the VR videos seems only 3600p ones need to do the "switch-on-then-off" trick. All other videos can be played immediately. Even the 3600p is running at 50-70fps, which is not bad at all for my GTX1080.
To check what you are having, go to "Apps" in the settings, go down until you see "HEVC Video Extensions from Device Manufacturer", then click on "Advance Options".