PvE content that has matchmaking matches players based off their power levels. Your power level is at 305 and thus there probably just aren't any players in the game at that power level running strikes. Most players in the game now are going to be 690+. Your strikes are going to look for players roughly 285 to 325 which at this stage of Destiny's life is going to be a very small pool of players. If you are having difficulty running through the strikes then I suggest going in with a fireteam from your clan or an LFG group.