It would help us help you if you say which HWH system you have.
You should be able to retract the jack manually in most cases. There are four styles of HWH solenoid valve that I know of. One cannot be released manually, but I think it's a pretty old style.
The other three have a 1/4" nut, a T-handle, or a lever to release the solenoid. Your owner's manual will show you which valve is which so you know which solenoid valve to release. The hydraulic fluid reservoir for the HWH system's vent plug (the one you remove to check or add fluid) might have a handy 1/4" nut driver built in if you need one, but you can use a 1/4" wrench or a socket on a finger ratchet (fastest) or a ratchet handle (still faster than a wrench). The 1/4" nut and T-handle get turned counter-clockwise until the jack starts to retract, but not too many turns (your owner's manual should say how many). The lever gets pushed so it winds up at right angles to the axis of the solenoid valve. In any event, after manually retracting a jack, I have closed the valve afterward. However, thermal expansion could cause a jack to extend far enough to activate the "jacks down" alarm in transit. In that case, you'd have to stop and repeat the procedure to re-stow the jack. This has not happened to me after three or four manual retractions, but you should be aware that it's possible with the valve closed-.
If you have a system with the old non-releasable valves, you will have to loosen a hyrdraulic hose to manually retract a jack. Hydraulic fluid will come out and make a mess you should be prepared to deal with so that it doesn't soak into the ground or screw up the pavement.
1976 Southwind 28', '96 Winnie 34WK,
2006 Tiffin Allegro Bus 40QDP