Hello,
We have a known limitation where map services cannot be used to perform filter actions in grouped value charts. We are working on a fix, but it didn't make it into the latest release.
As the other user mentioned, we just came out of beta, so accessing Dashboards from your content page now point to the new dashboards.
Can you let me know if there is a difference between opening the dashboard from the following two locations?
https://www.arcgis.com/apps/opsdashboard/index.html#/home
vs
https://www.arcgis.com/apps/dashboards
I am suspecting you are using a map service for your chart. We have known limitations with map services taking part in filtering other elements (like the map).