Greetings -
New user here, hoping some experienced users can offer some suggestions.
Vehicle is a motorhome, on a 2018 E-450 Super Duty chassis, V10, has 40k miles.

Driving down highway (rough roads) at 55-60mph.
Rig suddenly dies, all gauges go to zeros.
I get safely pulled off road, try ignition again - nothing. No crank. Gauges do not move.
Headlights turn on, normal brightness.
Crawled under rig, belts look good.

I checked and re-seated the four wiring harness connections on the fuse block under dash on drivers side (near the e-brake)

I also found a vid that says to try swapping relays in the fuse box (Power Distro Control/Center?). The relays are numbered starting at 63, and there are 4 our five on them in the fuse module.
But, I cannot pull them out like a normal blade-type fuse.
Its an awkward reach to get to it, because of the rv's front cowling/cover to get to the engine. I got a bit of a grip on the relay with a pair of plies, but they don't seem to want to lift out, and I did not want to make things worse by using too much force. Aren't these square (1 inch x 1 inch?) relays suppose to just lift out with a little pressure?

The motorhome also has an "Emergency Start" switch, where if your chassis battery dies, you can use the "house" batteries to start the engine. Using this "emer start" switch, I can hear two clicks like a selonoid/relay clicking, but nothing more.

Any suggestions would be greatly appreciated.

Thanks!