Unplug the appliance first.
Drain the water out manually either through the filter or by dropping the drain hose as low as possible.
Once the machine is empty of water take the filter out.
Look inside the filter housing and you should see the pump impellor.
Use a long screwdriver and turn the impellor manually.
Check to see if there is something jamming the pump.
If there is, remove the item(s).
Plug the machine in, set it to a drain or spin programme and watch at the filter housing to see if you can see or hear the pump running.
If you do, put the filter back in and try the machine again.
Hope this helps
Let me know how it goes or if you need more help.