Md. Code, State Personnel and Pensions § 28–306.1

(a) Except as provided in subsection (b) of this section, a member may not purchase service credit under this title if the member is separated from employment.

(b) A member who is separated from employment may purchase service credit under this title for a leave of absence approved by the Board of Trustees under regulations that apply to all members, if the member purchases the service credit within 60 days after the expiration of the leave of absence.