I've published a simple style from Pro to ArcGIS Online for testing. It has just one point symbol created from a standard shape marker in Pro symbology. I added the style to a Group and made that group the default 2D web style group in my organization's settings.
I added a point layer to a new map in Map Viewer (new, not Classic) and went to the Style settings, and the uploaded style was listed. However, when I try to load its symbols, the interface just spins and spins. Screenshot attached.
Not sure what I am doing wrong.
I am following the guidance in this blog post.
https://www.esri.com/arcgis-blog/products/arcgis-online/mapping/use-published-2d-symbols-in-arcgis-online/
@RussRoberts