I have received this error three times in the last month or two where I am unable to save my map. I cannot determine what caused those errors but I get the same message every single time: Failed to save map. The layer [MAP NAME] cannot be saved. Please see the screenshot below. The only thing I did before this was add new fields to the layer directly in ArcGIS Online.
This is an extremely frustrating error and this specific example requires me to redo a lot of work including recreating the web app, repointing my Survey123 to the new map, and all these other steps.
Is this a documented bug and/or is there a solution?
EDIT - I found a workaround where saving in Map Viewer Classic fixed the save issue. However, this would not work in all cases because it would remove Smart Forms functionality. Still interested in a better solution or more clarification on the error.
I have had a similar issue. When saving I receive this error, "