Preview Image

Hey there

I recently uploaded video files and preview images and everything was fine.
today I did the exact same thing, but the preview image isn’t showing.
Naming convention:check
location: check
permissions: check
thumbnail in WP: check
appoved upload: check
emptied cache: check

still not showing… ?!?
Same in Safari, Iphone, Chrome. Video is playing, Preview Image default.
in Firefox the videos do not show up at all! different issue…

I searched the forum, the web. I have no idea how to solve this.
Help is very much appreciated!

https://www.ads-software.com/extend/plugins/cool-video-gallery/