There was a problem reaching this app

Hi, 

I'm trying to add a report to a private chat in Teams, but am receiving the following error: 

I can confirm that this user has read access to the report and the data set, as they can access it online with no problems. 

Both myself and the user have the Teams app enabled for use in a Teams permission policy.

When I click the tab I am able to view the report within Teams:

Hoping someone can help! 

Thanks, 

Ben