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were you able to blow air through the grouphead side of the solenoid? as @Vince said I tend to let mine sit for 8 hours when I periodically clean. When I let my descaling routine slip, I have had to clear it as much as 3 times in a row, as any scale in the boiler that is dislodged can just flow straight in and block it again - or at least restrict flow. I know it feels tedious, but occams razor suggests it's still this..
I did that. I poked it with the needle and removed the limescale that was it. Still the result is that it does not work.