Has anyone had any luck adding an external .csv file via web URL in a Portal map? I tried to use a link to a USGS .csv file of earthquake epicenters via URL in a new mp on our Portal. Every time I tried to add it I got the error message "The CSV..., is not accessible and cannot be added to the map." The same thing happened when I tried to add a Google Sheet to the map. I was able to successfully add both sources to a map in our ArcGIS Online organization.
The goal was to have the map refresh from the source data every few minutes.
We are on Portal for ArcGIS 10.6.1.
Esri's documentation and blog posts on this topic mention ArcGIS Online, but nothing about Portal. Esri Support could not answer my question.