Smartview Essbase connection fails: Unable to connect to provider

We have a distributed servers set up with Foundation services, EAS, APS and FR installed on server1, Planning on server2, FDM and DRM on server3 and Essbase server component on server4. This was initially a new deployment of 11.2.3 EPM system which was later upgraded to 11.2.8 and 11.2.12 in-place.

This was again upgraded to 11.2.15 this week. The upgrade went fine and all the application components are accessible except for the Essbase connection in Smartview (both private and shared). 'Unable to connect to the provider' error occurs with both private and shared connections.

While configuring Essbase on server4, in the Essbase configuration screen, 'Enable Essbase' and 'Enable EAS' alone were chosen. Also, on server1, the old EAS and APS services are still there and were not removed after 11.2.15 configuration. Is it required to run the Essbase configuration on server1 as well (perhaps 'Enable APS' would be chosen on this server and the provider services would be reachable). Also, what will happen to the Essbase configuration on server4 if Essbase is configured on server1 with 'enable APS' (Essbase was never configured on this server before)?