One problem with hiding the ribbon is that it makes it hard for the user to refresh the data. Certainly the Refresh data when opening the file or the Refresh every 60 (you define the number of) minutes settings in the data sources can help with that, but there are plenty of good reasons for a user to want to be able to refresh data on demand. Pressing Alt + F5 on the keyboard will also refresh all, so that is an option when the ribbon is hidden.
You can put a note in the sheet to remind folks how to complete an on-demand refresh with the button or with Alt + F5. We've tried to minimize the effort on the part of the user, but we are asking users to interpret and make decisions based on the data in this dashboard. Learning to click on the Refresh All or a simple keystroke combination button should be within their skill set.