Same here... It was working for about 2 hours, then just decided it didn't want to anymore. I noticed that the editing ribbon, create pane, and quick toolbar are not always in sync when I select from either or. Incredibly frustrating for it to suddenly stop functioning. Same selections, as original poster... Only selectable layer is the one I want to trace. removing other layers doesn't help either, and if it did that would make the job a little harder, being unable to reference layers. My personal solution is to use ArcMap instead, but that is not sustainable. Forgot to mention... ArcGIS Pro stalls out often using this function.