Conversely, Article I Section 2 Clause 3 makes it explicit that only States have Representatives. There are only three ways for the district to vote for Representatives constitutionally:
1) Retrocession to Maryland
2) Admission as a State
3) Pass a Constitutional Amendment
4) Political retrocession. Let residents vote in Maryland federal elections.
5) General political retrocession. Let residents vote in the federal elections of the State of their choice.
6) Combination of Maryland, Delaware, Virginia, West Virgina, and District of Columbia in a single State.
7) Statehood for Montgomery, Prince Georges, Arlington, and Fairfax counties, Alexandria, Falls Church, Fairfax, Washington, and Georgetown cities.
Neither Maryland nor DC is in favor of retrocession and while the consent of DC is not needed, that of Maryland is.
DC is simply too dependent on the Federal Government to be granted Statehood
The Constitutional Amendment route was tried once before, but only 16 States approved it before the Amendment expired. Still it could be tried again perhaps without a seven-year limit to let the idea percolate longer.
The issue has never formally been presented to Maryland. It could include the incentive to take Washington back, or the capital moves to a more central location.