Hi,
First do the basic checks like whether the cube is having aggregates, indexes are green and the requests are compressed.
Go with a trial and error method.
First let the data run on an aggregated level means run the bex at company code or sales org level.
If you are getting the output. Then starting putting the other characters. Follow a top down approach and check at what level the query is getting dump. You might get a clue there itself
Regards
Gajesh