I have published a feature service that includes a spatial count locations layer and a related table with traffic counts for each location. I am trying to create a one-to-many joined view layer with the count locations as the target layer and the counts table as the join layer (see screenshot below). I've tried both inner join and left join, and both fail. Any ideas what could be wrong?

The reason I want the joined view layer is so that I can use it to populate the serial charts in a dashboard. They are currently populated by the related table alone, but I can't use the map extent to filter them with this configuration even though the data in the tables are related to the features in the map. I guess I can republish the related table to include geometry, but I'd rather not because it's millions of records and I'm trying to keep it as small as possible for storage and performance reasons. Note that the map and dashboard are on ArcGIS Online. The data are shared from Enterprise to AGO via a distributed collaboration. I'm trying to create the view layer on Enterprise.
Any advice is welcome.