Whenever you receive a PvP restriction (which includes Gambit) there would have been a banner that pops up when you log in that explains why and for how long. If you dismissed that banner without fully reading it then unfortunately there is no way to find out why or for how long. If it is your first restriction then it will likely be a two week restriction. If this isn't the first time you've received a PvP restriction then it could be for two months or longer.