I mistakenly filed as a Maryland resident and need to refile as a DC resident. How do I do this and get a refund from Maryland?

You cannot use the online version of TurboTax to file previous year's tax returns.  The current version of TT Online is good for tax year 2023 only.  If you wish to use TurboTax to file for previous years, then you must purchase the appropriate CD/Download version of TT, which you can find here:

TurboTax® 2022 Prior Year Tax Prep - File Past Years' Taxes (intuit.com)

If your DC withheld taxes exceeded your DC tax liability for those years, then you will not be subject to a late filing penalty.  Otherwise, see this:

https://otr.cfo.dc.gov/node/388782

DC and MD have tax reciprocity for wages and salaries.  If you live in DC and work in MD, then you should file MD Form MW 507 with your MD employer.

https://www.marylandtaxes.gov/forms/current_forms/mw507.pdf

Q. How do I get a refund from Maryland?

A, You file an amended MD return.