Thta error means MapViewer is not running or OBIEE has not been configured to use a MapViewer instance or the MapViewer URL specified in instanceconfig.xml is different/incorrect.
Will need some more details.
If your BI (analytics) URL is say
my.biserver.com:7001/analytics then is the mapviewer available at
If not then was it not deployed with OBIEE or is there a setting in instanceconfig.xml for a remote mapviewer instance?
If mapviewer is working fine (i.e. my.biserver.com:7001/mapviewer shows the welcome page) and you created the themes, maps, and tile layers in the same database instance that MapViewer is configured for (i.e. has a datasource for) then can you see the themes, maps, tile layers in the Metadata page of the mapviewer admin console?