Before anything else, can I affirm you did some basic troubleshooting in your attempts?
- the ID this time has not expired
- images and its text are clear
- all four corners of the ID can be seen
- information on the form matches with the ID (if any)
- no multiple attempts in a very short period of time
If so, what about asking their support? what did they say?
I've no idea if this exist in bitstamp but some exchanges have a manual verification in case their automated verification does not work. Try to see if you can request it if everything else fail however, I would imagine it would take long