as a side effect bug (surprise surprise!) of the new city reshuffle feature, which auto drops / adds citizens based upon thier residence (you can no longer be a citzen of more than 1 city), some 'valid' citizens have had thier citizenship revoked and will need to re-declare.
I have looked down the list and the only ones I can see that (still) need to to this are:
Audie Martin Einia Cargill Nixy Nilky
I know the last 2 is a vague hope
I would also like to remind you all to declare all your characters as citizens if you can as it helps us to keep the features to which we have become accustomed and continue to be a fine metropolis and reseearch centre.