Why am I having a problem with draining with BEKO DE 3430F?

I have a brand new (less than one week) Beko dishwasher which isn't draining. originally we had a hose extension which was too long, there were kinks. we bought a smaller extension, and have installed it in exactly the correct way that it wants, but it won't drain. Originally it took the water in but wouldn't drain, not it seems it won't do either, presumably since it won't take in water while there already is some in the pipe.

Any help would be greatly appreciated,

thanks