1. While communities allow portal users to view Dashboards, Salesforce doesn’t allow community users to refresh/schedule dashboards.
Our org has hundreds of community customers and it’s not practical to create one dashboard for every customer - so they created a dynamic dashboard “Case Dashboard”. However Salesforce also does not allow dynamic dashboards to be scheduled for a refresh - even by admins.
Allow automatic refresh of “Case Dashboard” when a portal user runs that dashboard or goes to the dashboard page.