To the rear of no. 46 is a window and French doors. As those openings serve one room, then the LPA can decide which opening to take. The new dwelling (no. 46a) breached the 45 degree line line from the French doors but was acceptable from the window, which is why it was approved. Your proposal breaches the 45 degree lines from the French doors and window, which is why the LPA are stating is the issue.
So your options are to withdraw or allow the application to be determined. Bear in mind that the former will not provide you with a formal decision to Appeal, nor will you have the Officers’ Report to cross reference to.