The E20 code indicates a drain issue. You need to check the filter. To get to it, please, open the small square door in the lower right corner.
Prepare a water receptacle (a bucket, bowl, etc.) Pull out a small grey hose (not all machines have it!). Hang it over the receptacle. Then remove the cap and drain water.
Then remove the filter and clean every part of it. Check the filter housing and ensure there are no debris or foreign objects at the back of it, where there is the pump impeller.
Put the filter back and restart your machine. Most likely, the problem will disappear.