Are you trying to embed a canvas app in a model driven app and seeing this error – “We are having trouble displaying this app”?
There is a Canvas App Entity/Table that the user needs ‘Read’ access to. To provide this access, navigate to
Advanced Settings -> Security -> Security Roles -> <Security Role Name> -> Customizations -> Canvas App -> Provide Read Access at Organization level
Screenshots below –
After you have followed the above steps, refresh the model driven app and you should see the embedded canvas app.