Context: I am using a python script to create view layers of a master layer for each jurisdiction in my state. This script was successful and I've been working with the view layers in the Map Viewer without issue. I've been using AGO Assist to copy the formInfo from one layer to another and it has been working. I have a current map with multiple of these view layers in it, with the forminfos copied successfully.
Problem: Randomly (at least I couldn't identify any change that made this happen), one of the layers disappeared from the map and when I try to re-add it, it says "Unable to add layer." When I go to the layer's data page it says "There was an error."
Attempted Solutions:
1. I have actually been able to add the layer as a web service -- but I'd rather get to the bottom of this rather than use this solution.
2. I have deleted the layer from AGOL and re-ran my script (which only creates view layers that don't already exist, so it only created the one that I deleted). In the new version of that layer's data page and I can see the data that's supposed to be there -- but then once I try to add it to a map viewer (either from the map or from the item's page), I get the same error "Unable to add" and now the data page is showing "There was an error" again.
3. As far as I can tell, the url for the web service is the same in AGO assist and on the items page (something I found as a potential solution in a different but similar question)
I'm guessing something I did in AGO assist is what broke it since it was working and then all of a sudden it wasn't, and I'm not having any problems with other view layers (through spot checking -- there's about 300 layers so I didn't check them all).
Any help/ideas/suggestions is MUCH appreciated.
