I have spent a solid 8 hours developing arcade statements from a service with a one-to-many relationship (Census PUMAs and an aspatial table). I used arcade statements to quickly summarize related tables without having to transform the data into a flat file and used the expressions to create multiple charts. The popups behave as expected in the web map and AppBuilder, but will not display in Dashboards. Strangely, they DO appear in Dashboards beta. Any advice would be greatly appreciated.
The documentation indicates Dashboards beta has ‘greater’ support for Arcade expressions. It might be your (complex) arcade expression cannot be rendered in operation Dashboards? Not sure if operation Dashboards supports arcade expressions at all; whether in a dashboard item or pop-up in the map.
I think it's simpler than that. Operations Dashboard soon will be phased out. Dashboards beta is its successor. Dashboard beta simply has more capabilities than operations dashboard. I don't think operations dashboards is being updated anymore. Arcade has. Operations dashboard did not update with the latest arcade possibilities.
That is my guess...