If you have your USB in the printer. Can you access the time lapse video VIA Bambu Studio? Click on Device at the top. Click on Storage on the left. Make sure Timelapse is selected in the top center. From there you should be able to see your timelapse files and click on download of any that are availible.
If not I would try and do a USB format from the machine it self when you don’t have a current print in progress. NOTE: you will loose any files on that USB stick. Make sure you don’t have anything on it you don’t want to loose.