Tony Stark signed the Accords but then got written off as unstable after having a few outbursts at his tower from his flashbacks from his fight with Steve and Bucky. In other words the fight that left him freezing and half to death with no way to leave, until Black Panther found him. So S.H.I.E.L.D. seized his possessions. Now the only way be can still be Iron Man is under S.H.I.E.L.D.'s strict rules. One if which is no fraternizing of any kind which anybody affiliated with S.H.I.E.L.D. but one technician catches his eye.