I drained it at the filter, when level falls it goes into drain mode so pump will work and no blockages. I checked the pipes for blockages, a bit slimey but all clear.
Code coming up as E20 but have followed advice from earlier posts and gone into engineers mode which shows code E21
Have you just connected it on a sink spigot if you have then this may still be capped off . If you can hear the pump churning then it has to be a blockage if your sure the drain hose is clear and the sink spigot is ok then it must be a blockage in the sump hose (between the tub and pump manifold) .