Lotus Maximus pump problem

Sorry about this chaps, I'm new to this game and have what I think must be a
common problem.

I've wired my pump and filter up switched on and...................
the fountain, fountains but water isn't being pumped to the filter.

I bought this set up on the internet and although it was efficiently
delivered, no instructions were included.

I've tried restricting the flow of water from the fountain in the hope that
this would send more to the filter but this had no effect.

I can't see any adjustments I could make to the pump and have run out of
ideas.

HELP!

Regards Nick