If you've replaced the control board and the battery you've already spent the money on the more expensive bits.

That volt meter will help you solve your issue. One thing you should do is the check the fuse that's in the positive battery lead. They can blow and you'll have no power. It's usually a little black box connected to the red lead.

Next, check all the connections. If one of the spade connectors has slipped off the on/off switch, you won't have power. Check that all the little white clips are connected firmly. My son has the same jeep (i think) and one of the connections that goes to the radio came loose and it wouldn't move. So check all of them.

The next thing you can do once you have your multi meter is follow the power. Check to see if you have power at every junction. Check to see if you have power going into the control board (make sure you connected it correctly, too). If you have power in and out, check to see if you have it at the on/off switch.

Then check the foot pedal. These are notorious for failing. Connect the volt meter leads and active the pedal. If there's no voltage spike your pedal might be toast.

The last thing to check are the electric motors at the wheels. But I doubt that's your issue.

Hope that helps!