if there is a phone number on the notice, call. if not, write them at the address indicated, send by a method where there's tracking so you know it arrives. then tell them you are a full-year PA resident and that by MD law exempt from taxation on wages earned in MD. Ask them what you need to do to verify your residency in PA to resolve this matter. you may also mention you misfiled that prior year because you were a full-time PA resident at the time. Depending on the year you may be able (and want to) to get back those MD taxes but then would have to file an amended PA return to eliminate any credit you claimed for MD taxes. don't know which way you would come out ahead in that prior year.
