Problem with the board card

Hello
We are currently building an Openrov 2.8 and we have problems turning the rov on. We did every step of the building tutorial but when we try to connect the batteries to the cockpit and the motors, nothing turns on.
Moreover, when we connect the first battery, the board card turns on for 1 second and then, everything shuts down. The power and Ethernet lights turn on for 1 second. Also, when we mesure on the card we have a 10V tension.
When we turn the cockpit on the computer, the video is on but we can’t move anything.
Did someone had this kind of problem ?
Do you know where this problem could come from ?

Thank you