Where your dashboards defined using the Windows app or using the web app? What sources do use in the Dashboard? Does the web map that you use draw in ArcGIS Online or Enterprise? When was the last time that your Dashboards open? Before or after Thursday, April 12th (date that ArcGIS Online was updated)? Did you already contact Esri Support?
My dashboards are defined using arcgis online web app, and they are hosted on our enterprise system with the County of Riverside. Last time I checked them was April 12th.
