Operations Dashboard should be able to generate server side statistics using layers that have a join. Can you check the network requests (via the browser developer tools) to see what the error code and message is?
If you still experience issues, you can reach out directly to the team at Dashboard4ArcGIS@esri.com or by opening a technical support case.
Can you open the "Network" tab, this will let you see the requests sent to your server. Then try to add the visualization using the layer that gives you an issues. You should see requests like "../FeatureServer/query". Click on one of those and then click on the "Preview" sub-tab to see the full response.
It should look something like (yours probably will have an error):