You should reach out to DHCD. There's a form on their website to start the resale process -
https://dhcd.dc.gov/sites/default/files/dc/sites/dhcd/publication/attachments/2022-7-25%20IZ%20ADU%20Resale%20Price%20Request%20Form.pdf%20%28Fillable%29.pdf.
They will provide the maximum resale price and help find a qualified buyer.