I have configured the Fiori Launchpad Service and configured the on-prem S/4HANA 2020 as the content provider. Exposed the apps to Launchpad service using a business role. I can see the apps in the Launchpad service but when I open the apps, I am getting the message " Forbidden". The same apps are working on the on-prem launchpad.
I raised an SAP incident and my issue was resolved by SAP. The reason was, there were additional parameters in the destinations (Design-time and Runtime). When we create the destinations(Design-time and Runtime), we should follow the steps in below URL.
Trying to look into different perspectives here. Perhaps a specific Web dispatcher or a business role not set up correctly?
Anyway, take a look at these as it can help as a health check to make sure you did not miss any steps.
KIndly advise if it help to address your topic.