habbyguy

If you can hear the pump running (pretty easy to do, if it is) AND it's still got plenty of fluid, AND you can verify it's actually not trying to lift the tailgate (by stopping it midway and trying to get it to resume the lift as you supply just enough lift to hold the tailgate in place before re-starting the pump), THEN I'd suspect the pump is totally gone, and it's going to have to be rebuilt.

Just for giggles, when you refilled it, what did you use for hydraulic fluid?

mononen

So the pump isn't running when I try and trigger the switch. The only noise I get is the lock electronics opening the latch.

I used Pentosin CHF11s when refilling it.