if your opening handle from either outside or inside is tensioned you won't be able to activate the lever (move it to unlocked position), my guess when you installed it you have somehow made either one to hold pressure on it, take both the opening rod from the inside handle and check the opening mech of the outside handle (or take it off if you can), once that is not tensioned you shoud be able to unlock the door.
this is like when you have someone coming to your pass side door and pull the handle before you have a chance to unlock it, you can't and the handle has to be released before you can move it.
