Maryland Code, Corporations and Associations § 9A-1106

(a) If a foreign limited liability partnership is doing or has done any intrastate, interstate, or foreign business in this State without complying with the requirements of this subtitle, the foreign limited liability partnership and any person claiming under it may not maintain suit in any court of this State, unless the foreign limited liability partnership shows to the satisfaction of the court that:

(b) The failure of a foreign limited liability partnership to register in this State does not impair the validity of a contract or act of the foreign limited liability partnership or prevent the foreign limited liability partnership from defending any action, suit, or proceeding in a court of this State.

(c) A foreign limited liability partnership, by doing business in this State without registration, appoints the Department as its agent for service of process with respect to causes of action arising out of doing business in this State.