Hi Obinna,
Failed to get the cube from connection is a generic error message, and can be due to multiple reasons. Mostly the issue is associated with the BICS connection.
To find out the exact cause I would suggest you to capture HTTP logs using Fiddler.. Refer the below helpful blog that might give you a good idea on how to do that. Fiddler Logs
Dashboard processing and cache server traces might also provide an understanding as to what is causing the error.
Hope this helps.
Regards,
Niraj