Enable Attachments Not Working

[SidonyDunn]

Hi,

I am trying to enable attachments on a hosted feature layer but the 'Enable Attachments' button on the overview page does not work. I tried enabling it in ArcGIS Rest Admin using 'Update Definition' instead.

Attempt with Format set to JSON:

{
 "error": {
  "code": 500,
  "message": "JSONObject[\"dataset\"] not found.",
  "details": []
 }
}

This is the error message I got when I set the format set to HTML: 

Has anyone ever experienced an issue like this before? Any assistance would be appreciated. Thanks!