The manual will tell you how to 'null' the system but it had to be level first.
The system has a safety built in to prevent the frame from twisting. It sounds like you were out of level with the left side down. It will allow you to extend the left jacks to bring that side up to almost level but we t let you extend the right which could take the bus out of level even more.
I've had it where it seemed very picky about me being out if level and insisted a set of jacks be extended further before it allowed the jacks on the other side to extend.
Does that sound like your situation?
Chasing 70 (degrees F) in a 2004 Travel Supreme MH, 2015 Jeep Wrangler, mountain bikes, hiking boots and swim shorts.