[Richard]

Check the left side travel solenoid with the ignition on, and in travel mode. Please place support under the coach before crawling under there.

Is it getting voltage? Place a screwdriver or washer on it, it should stick if the solenoid is energized.
If it is getting voltage the internal valving may be stuck or occluded.

There is only one height control for the front. It essentially averages the ride height in the front and feeds equal pressure to both front air bags. If the left front air bag was not getting air, the HCV will try to raise the coach, but air is only going to the right side.