BINGO !

That's what many posted since the beginning: are you sure your LTS has all the required joins to be able to return data for your analysis?

The error page sounds like a "no".

So look at the error and identify what joins / granularity you are missing and solve it (by changing your RPD or removing things from the analysis).

As said earlier OBIEE first look at which LTS are able to provide an answer to the query (analysis), only after the priority group is used to define which LTS must be used (and if many the order is used).