still can't connect a dishwasher - what am i doing wrong?

Do it in this order: water, drain, power. Water supply first with the valve under the sink off, then the drain hose, and the electrics last once you know nothing leaks. The one that catches almost everyone: if the drain goes into a waste disposal, there's a plastic knockout plug inside the disposal's dishwasher inlet. It has to be knocked out, otherwise the dishwasher fills and won't drain. Also loop the drain hose up high under the counter so dirty sink water can't run back in. If it's hardwired rather than a plug, that bit is for an electrician.