What they forget to mention is..... you actually need two extensions for this to work. You need the "HEIC Image Extensions" and "HEVC Video Extension from Device Manufacturer". Install the both and you will be good to go!
I can't count the number of sites you will visit and none of them will mention the second extension. Actually, the Windows Store does state that the
HEVC Video Extensions is required. This extension can be purchased for $0.99. If you just get the HEVC Video Extension from Device Manufacturer, it is the same thing but free.