Sadly, you didn't give us enough information to even guess. You can't export, it gives the wrong format tells us nothing of use.
What's your computer system ... OS/CPU/RAM/GPU ... what's your media format/codec, such as ProRes 422, Sony Slog-3, DJI drone in mp4, what?
And what format/codec are you trying to export to?
It's good to provide screen grabs of your sequence and of your export dialog settings. Drag/drop them directly into the TEXT reply area of your reply, not to the 'attach files' area.
Neil