The high pressure hydraulic lines do not use O ring seals, they are compression fittings. It could be as simple as a loose fitting that a slight tightening will stop the leak. Many HWH jack system owners have reported bad hydraulic lines. Rather than wait for HWH to send another, you could remove the bad hose and take it to a local shop that could make you a matching hose at much less cost, time, and shipping waiting for HWH. It could also be a bad solenoid valve. You'll need to wipe up all dirt and fluid and operate the jacks to see where the leak is.
The shuttle valve that is attached to your pump can also leak, it does contain an O ring but I don't think it can be rebuilt by owner, it takes professional tools and measurements.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI