The Story Map Tour web application returns the error, "Save failed due to an invalid html tag in a name or description" if audio is added to an application configured with photos hosted by ArcGIS Online.
Last Published: September 24, 2014ArcGIS Online
Bug ID Number
September 19, 2014
May 31, 2023
After review by the development team, it has been determined that this issue is related to a known limitation with the software that lies outside of Esri's control. The issue's Additional Information section may contain further explanation.
This is known limit when creating MT using image upload workflow: the AGOL feature service that gets created sanitises HTML more restrictively than other workflows. It's the same reason you can't include the hr tag in the caption for an MT that is created using image upload.
It works OK if you use other workflows.
Configure the application using the custom options > Start a new Tour, and the issue is not reproducible.