Error "HTTP request failed" for Fiori App "Approve Purchase Order"

Hi Experts,

After assigning appropriate role to logged user, i am getting error "HTTP request failed" when I try open Fiori app "Approve Purchase Order". See the error in "Attachment".

We used the Option "Central Hub Deployment", in Detail to say, we have two Systems, one System consists of Netweaver Gateway as Frond End Server for accessing the Fiori Apps and the other System is the Backend System contains the backend data, that is, Business logic data used by the Front End Fiori Apps. It can be worked, in this way? Did I understood anything wrong?

Is there any Connection issues with the backend Server from where this App is trying to access the data?

Any ideas, please?

Thanks & best regards,

Sreenu