Many states bar associations have "title standards" that they use to "overllook" the situation as not being a problem for common nicknames - Stating that common nicknames are considered to be one in the same, e.g. Rob or Bob for Robert, etc.

An aka also works in most states, and as a notary, if you havea matching  ID and the person is willing to swear they are one in the same person, you should be able to notarize accordingly...but each state may have it's own peculiarities.
What do others think?  Jeanne