Yes I have to say that is my gut feeling - sadly. Will that shower tray have a flexible joint to the waste? Cant imagine how you secure the pipe underneath and then lay the tray down?
Dry fit the shower and waste so you get the trap in the right place. Undo the trap from the tray but leave it attached to the pipe. Fix the tray down with either a weak sand and cement mix or if your floor is level Silicon and reattach the trap from the top of the tray.
