Yendif Player

Using Yendif Video Share component on Joomla 3.8.2

I have two vids in a K2 article.
One is .flv with a .jpg cover. Plays just fine with the plugin code {yendifplayer videoid=2}

The other is .mp4 with a .png cover. Does not play with the plugin code {yendifplayer videoid=3}
I get "Unable to play media. Media format not supported" error message and the png image does not display.

This same video plays fine if I post the link in the browser address so it's not the video format that is at fault here.
videos are stored in " www.Mysite/images/videos/vid.mp4 "

I cannot figure out what's wrong. I can work around this by only uploading .flv vids with .jpg cover but I'd prefer mp4.

Do advise..

Yendif engine is set to HTML5 but the .flv plays just fine when its set to flash.

What gives. What do I need to do to get the mp4 to platy as well as the flv?
What do I need to do to get the png to display like the jpg?

Thank you.

If FLV works, then MP4 should work normally. It's really hard to get you a fix without checking the issue directly. Kindly share me your site link in where I can see the issue.