How do I force IMDBpro to properly show the intended Thumbnail in the video I upload?

I uploaded my video. IMDBpro showed random frame as thumbnail instead of the first frame in the video (It does the same random thing for the reel it extracts from reels in my various TV/Movie releases too!). Then I used different editing software(s) like even mp3tag and so on to create the proper thumbnail to show up correctly in Windows Explorer first. Then I uploaded again.

But IMDBpro is stubborn to chose some random frame. Extremely frustrating as I lost 2 days following up on various articles etc. 

Appreciate immediate help.