I have a layer with traffic signs. I noted some missing symbols and updated it in my ArcGIS project, then overwrite my hosted feature layer in AGOL to update these symbols as well. The symbols updated properly in the hosted feature layer but no on the Web Map (map viewer).
Note, I did the overwrite by checking "Use symbols types compatible with all clients in Pro before publishing".
The symbols could have been downgraded when you checked on Use symbols types compatible with all clients in Pro before publishing" or the layer item or web map has a symbol being used vs. what exists at the service level. I would have to check out the map/layer to verify this.
