The Pilgrims led 1-0 at half-time courtesy of Nicky Walker's fifth goal of the season, but were pegged back by a 58th minute header from Courtney Meppen-Walter. United subsequently required some fine saves from George Willis to preserve a point, although Andi Thanoj did rattle the crossbar in the dying moments.
United's afternoon ended on a sour note when debutant Jordan Thewlis left the pitch on a stretcher with a serious-looking ankle injury.