Did you enter your SSA1099 in the right place in the federal return? Information flows from the federal return to the state return. If you entered the Social Security in the wrong place, that might be why you are having trouble with MD. Maryland does not tax Social Security.
Look at your federal software:
Go to Federal> Wages & Income>>Retirement Plans and Social Security (SSA1099 and 1099RRB) to enter your SSA1099.
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