Video upload problem

Hi,
please describe further where you want to upload the video. What do you want to achieve?

Your video doesn’t appear there because you can only choose images there. As you say it’s the “featured image“. You can use a slider for adding videos into the header of posts.

Can you please send a screenshot from the backend of one of the posts you have a video set there?
Do you use a plugin for this? As far as I know this is not the default behaviour and therefore nothing was changed on the side of Meteorite.

Sorry, but I don’t understand what you want to say with these screenshots.
Which plugins do you have activated?

In the two screenshots you posted before, I cannot see where the video is that you mean.
https://prnt.sc/1o7qfgf
https://prnt.sc/1o7phfl

Also on the page you linked above I cannot find a video as featured image: https://tuyograf.com/sosyal-medya-tasarim/sosyal-medya-tasarim-ornekleri/

Where exactly is the video that you have set as featured image?

The grid system and therefore the presentation of the posts and videos come from the plugin The Grid you have installed. Therefore you have to look on your own how you have to set up your posts so that they show a video. As this is not my plugin and is not a free one, I cannot further assist you with this topic.