If you receive an error stating the Last Name is Required, this is a remnant of an old Bug that was resolved in an earlier build of GIFTS Online. This may still occur if your form is very dated - you will likely need to build out a newer version of your form.

As for the error itself, this can be corrected by contacting Blackbaud Customer Support at 877-704-3343 or creating a case through CaseCentral.