Hi and welcome to the forum,
I tried using Rain Down Spout 3 myself but had no problem rotating it, in the plan or 3D view. Maybe I have changed the Snap Edge settings at some time in the past. The Snap Edge setting (on the Behaviour tab), will force an object to align to the wall, depending which edge is selected.
If 'Back' is selected it should automatically snap with its back to the wall. If Front was selected then it would be back to front but, in either case, attempts to rotate it would not work. If changed to 'None' it should freely rotate. If Collision (Status bar lower right) was ON this could also stop it rotating, if it would collide with something when rotated.