I'm the pp above you. I kept trying and finally got all the way to the end just now. But I got the below message. I clicked "yes" when it asked me about qualifying medical conditions (I qualify under two of the ones listed). Based on the below message it seems like the portal hasn't been updated to let the medical conditions through to an appointment though.
Thank you
COVID-19 vaccinations are being made available in phases to ensure those populations most at risk and essential societal functions are prioritized. Currently, vaccination appointments are only available for District residents who are 65 years of age and older and/or occupations listed on coronavirus.dc.gov/vaccine. To receive alerts when more appointments become available or open to new populations, sign up for notifications at vaccinate.dc.gov.