make sure you are in Data View.
Guess I'll throw my hat in the ring.
ArcMap 10.2.2.3552, have a gdb feature class that will not snap in layout view on two different maps, but will in data view. Guess this has been an on-going issue, didn't notice til I had two seperate maps open, one in data view and one in layout. I couldn't snap in the layout view, ended editting session switched to the other map document, then open editting in the data view map and snapping worked no problem! Closed editting session, changed that map from data view to layout view, opened a new editting session, and no snapping again. GDB feature class has ~850 polygons in it.