Teams - Viva Learning - Add to Calendar Error

Hi everyone, we have the Viva Learning module active in the on-prem teams app. Our Viva Learning is connected to Linkedin Learning. We use an on-prem Outlook exchange.  When viewing a course and attempting to use 'add to calendar', we receive an error: "Not able to fetch the event details. Click on Add to calendar to try again".

Any thoughts on what might cause this error? There is no error code or additional details.