That web page works poorly. It times out too quickly, making one start all over again. The appointment link sometimes fails to function. Then one may phone the complaint number, and go through 3 different operators taking an half hour of being on hold, if one has that much patience, to finally get an appointment accomplished; that is, if the call isn't dropped. Then one simply starts all over once more. No problem!
I was there Saturday to book an appointment and the next one was in mid-July. If that works for you, the reservation site is accessible from this page once you create your documents list. http://license.mva.maryland.gov/CheckList/default.aspx
Thanks! Your answer is awaiting moderation.