Well, I hate to be this person, BUT..
IS ANYONE ELSE HAVING PROBLEMS PUBLISHING LAYERS IN A WEBMAP? OR WEBLAYERS?
To me, it feels like since they updated AGOL this month, some of my layers that used to publish seemlessly are now not loading, with an error that says "Unable to add layer. Feature layer must be created with either a URL or a source". If I export the feature class to a new dataset, it publishes. I can change the fields around and it will publish, but the second I import symbology to the layer - "Staging Failed" when trying to test publish web layer.
So so frustrating. Why can't I publish a layer with imported symbology? Even before I started importing symology on exported datasets ... suddenly my layers stopped publishing. Yea the layers were renamed (just the alias!) but this is too much.
I have not been experiencing any issues specifically since the update, but I've seen "Staging Failed" plenty in the past.
Can you share more about the layers you're attempting to publish, where the data is coming from, etc? And if the imported symbology is somehow related, what exactly do the symbology settings look like?
Also, with your mention of a "new dataset": are you trying to overwrite an existing layer when you publish?