No option to add field to related table in ArcGIS Online Feature Service

[AaronWorthley1]

I have a related table in an ArcGIS Online Hosted Feature Layer, originally published from Pro. I'd like to update it with a few new fields, but there is no option to add field in the Feature Layer Item data tab. Tried adding via Pro-Design/fields and Add field Geoprocessing, but both fail.

[GIS_MJ]

I have the same problem.  Did you find a solution?

[AaronWorthley1]

I have not. No response to the inquiry here, and haven't had time to deal with ESRI support. If you stumble on anything- please let me know!

[Anonymous User]

Hi Aaron Worthley‌,

The tool is likely failing in Pro because of this BUG, fixed at 2.5 (releasing soon): BUG-000124062: The error message, "Error: [999999, Something unexpe.. 

Not seeing any issues logged for why Add Field is missing from the related table in ArcGIS Online. I know you mentioned above that you haven't had time to contact support - if this is still occurring I would definitely recommend getting a case logged. 

Hope this helps,

-Peter