This is what I did... I did this last 2 years in a row. I have slightly different problem. I just cleanned out the hose a about a month but still did not work... why? the reservoir had stuff - gunk in it.
I did the following:
1. Loosen the gunk inside the reservoir. I got a coil. I shaped it in zigzag pattern and hooked it up with my drill. I put the zigzag patterned coil end into the reservoir and ran the drill for a few 10 -30 seconds in slow speed. I tried to loosen it at different depth.
2. Wash away the loose gunk by letting the water rise up in the washing machine tub. You can watch the water level rise. Stop when it reaches the top of the reservoir. Then unplug the hose. Plug in your own hose to the reservoir and blow air fast and hard into it. It will blow out the losened gunk into the washer tub. Do it several times. Then put back the hose and spin out the water.
3. Repeat above 1&2, if necessary. I did 3x.
4. I also cleaned the hose to the reservoir tube.
Good luck. Hope it is helpful.