no video thumbnails, no response to posts

Bridge is no longer generating thumbnails for h.265 files.  Its obviously capable because it might do one or two in a folder. 

Seeing as "thumbnail browser" is a core function, you'd think there might be some response from adobe - but I've just searched the forums and all the posts I've found had zero replies.

I have cleared cache, media cache and files, tried software rendering. Nikon and DJI 10 bit Movs. 

What is the point of this product if it cant even do its core function? Its just face-mashingly frustrating