Sharing Dashboards Externally

I've successfully created a dashboard that contains Pro Content and would like to now share it with one of customers outside of our organization. It contains no RLS, and Power BI shows that I am able to share the dashboard successfully with the customer. The customer also has a Pro Account and receives the email notification that a dashboard has been shared with them.

However, when they click the link in the email, they are directed to the page below where the PBI logo appears to be giving a "loading" notice, but the dashboard never loads.

I've tried it in several different browsers, but with no luck. Has anyone encountered this before or have any potential solutions?