I struggled with this. The FVP is pretty fussy from my experience yet some other users have no issues.
If you can, format the stick using the FVP the downside is that it is NTFS and many other devices are still using FAT32.
Otherwise try other sticks/cards. I had one stick which my unit always refused to perform a firmware update from.
From memory the transfer tends to be a long while but not longer than the duration of the actual recording.
When the circle thing stops rotating in the screen corner the transfer is complete. You can leave the recordings screen and return to check.