I understand that in January 2017, the deputy First Minister of Northern Ireland, Martin McGuinness, resigned, and due to the way the devolved government of Northern Ireland works, this forced the First Minister, Arlene Foster, to resign as well. This then led to an election in Northern Ireland in March.
Why has that election not resulted, to date (June 2017), in the position of First Minister being filled again (presumably by the leader of the party that won the most seats)?