Hi,
This might be the problem described here: Video exports producing 0kb files on Windows 11
If so, follow the steps in that article.
You may also want to check that your D: drive has enough space for the video. if it doesn’t have enough space, then the video will be empty.
If neither of those seems to be the problem, contact support at https://twinmotionhelp.epicgames.com/s/ and share a copy of the Twinmotion.log file (Where to find Twinmotion .log file) from your export attempt. The log file should contain error info about the failed export.