Try testing the motors for the grounding issue that they mentioned; if you have trust fire batteries, they may be the culprit and I may have a solution below, but if you have the lifepo4 batteries, it is not an issue.
The trust fire batteries have problems with built in circuit protection that failed in one of my batteries. Turning on the ROV would trip whatever tube it was in and I would get no power, and then it turned out to be too much draw to run it off of just one tube.
Check to see if you are getting readings from BT1 and BT2 in the information on the right side of the screen, that means both tubes are working. Also pay attention to what it says as you move the motors in and out of the water, if it goes crazy high it may be causing the system to trip.