If you open the door is there still water laying in the bottom of the dishwasher?
Ok did it drain the water out itself or did you scoop it out by hand?
Ok so if you set it going on a cycle now the first thing it should do is bring the drain pump on. Then after a few seconds or so it will start to fill.
Do you hear the pump running?
If not then is this when you hear the humming noise?
Ok the humming noise you hear sounds like a blocked pump.
What you can try first is remove the bottom basket and take out the filters and the mesh filter.
Then look inside the sump and at th bottom on the left is a cover. Its held on by a screw (star shapped).
Remove the screw then you can remove the cover.
In there is the pump impeller. Check theres nothing stuck in there. But be carefull as its usually glass that blocks it up.
Make sure the impeller turns ok. Then refit the cover and screw and retry it and see how it goes from there. Fingers crossed this wllill cure it and get it up and running again for you.
But if you cannot clear it that why then the dishwasher will need to be pulled out and panels removed to access the pump from there and remove it and check it from there.
Ok the impeller does ping round in stages so you may feel a bit of resistance on the pump impeller.
As to accessing the pump. What you can try first is remove the outer door panel.
Then below the door you will see a metal panel above the plastic base, You need to remove this.
Then with that off you will see a hose on the far left. Pull this off.
Then you will see the pump. You need to twist it off and remove it from there and then you can fully make sure the pump is clear.
Then you can retry it from there and see how it goes.
But i must warn you its not the easist job to do if you havent done it before as there isnt much room in there to work in.