How To Refresh When Power BI AND Data Are All On-Prem?

Hi -

We're running Power BI report server on-prem, and all of our data is on-prem, too.  Almost all of our reports/dashboards are live-connecting to our Analysis Services tabular cubes, so we don't have to worry about Power BI refresh.  However, we have two small reports with very disjunct measures that make it very difficult to work with a live connection, so the reports were designed with specific MDX queries that pull the data in.  The problem is getting them to refresh every day after the cube is done processing.

When going to "Manage" the "Refresh Now" button is greyed out, and we always get a generic error when trying to set up a schedule.  Even though I belong to an administrator role that has all privileges, I can't create a schedule and the "Refresh Now" is greyed out.

Do we need a gateway for this?  I was under the impression that the on-prem gateway was just so the data could be local while Power BI is in the cloud, and as previously stated, both Power BI reports and our data is on-prem.

Any help is greatly appreciated.

Thanks.

-Phil