That's appalling!
I hope they get it sorted and kick up a fuss if the result is close. I know from my DS that some first time voters were confused.
DS lives in halls of residence and the uni registered them, but some students living in private rentals weren't registered. I got DS to double check that he was registered, but I guess some parents aren't so "controlling". I had to intervene and get him registered for the referendum. He had assumed he was registered, but he wasn't and we had to act quickly to get him on the electoral roll.
DD has lived in a number of short term tenancies and could easily have missed out on being registered. Again, I've nagged her and she did have a vote, but I can imagine that some people are more laid back than I am.
Students can remain at their parents' address and apply for a postal vote, but the situation isn't explained very clearly. I'm not surprised that some of them miss out and it doesn't help if the local council isn't on top of the situation. I'm not really blaming the councils either, because I know that they're experiencing cuts and don't have the time to follow up absent voters.