The only two things that have happened since I last edited City Limits are: I upgraded to pro 2.6 and we installed a new version of license manager.
1) I tried to edit city limits in an existing project map, it failed with error. I closed arc pro.
2) I restarted my computer, I created a new project with a blank map added parcels (SDE), cities (SDE) and Zoning (SDE). I could edit zoning but still can't edit cites, I tried to split and edit vertices. I am working in ArcGIS PRO, there is no such thing as an "editing session".
3) I am in the correct coordinate system, no error in the editing content panel
4) Edit status dialogue says the feature is editable.
Any ideas I haven't tried?