Hi.. let me see if I can help..
it would not be considered a leak... if the water is not going down the drain... it would be a back-up... I suppose... either way, lets see what the issue is.. you state there is a drain solenoid valve in the drain line... during the normal operation of the unit that drain should open.. have you witnessed it opening and no drain...or not seen it open at all....
you also state you cleaned the line, I take that to mean from the interior to the solenoid valve?
you cant clean the line if the valve is shut... so... what we need to discover is, if the solenoid coil is getting voltage and is not operating... you can do that by taking a volt/ohm meter and with the unit unplugged or turned off at the breaker.. remove the leads from the coil and check for continuity across the coil.. if no continuity.. then the coil is open... bad solenoid valve.. if you do have continuity ...we need to see if you are getting the required coil voltage at those leads.
you would leave the leads plugged into the disconnected leads from the coil and operate the machine as usual and note when the drain should open if you get the voltage...if you dont then we have a control board problem.. if you do get voltage and your coil reads good..you may have clog after the valve in the piping... the valve opening but no fluid can flow...this is common if there is any piping that might considered not going down hill...like a trap or a section of drain pipe that goes up hill before going down to drain...bacteria can grow and clog the pipe...
get back to me on what you find so i can help further..