Looks like a first post, welcome to IRV2
I'm assuming that it is either ISC (8.3) or possibly the ISL (8.9) engine, as I don't recognize the ISP? In this year, this should be a CAPS vs just a few years newer VGT engine.
If it was working just before taking out the batteries. You might try disconnecting the negative and waiting a bit, then reconnect and see if this might 'reset' things. Simple to do, and who knows...
Another thing to look for is some chassis have an inline fuel filter that is easy to miss, inline prior to the lift pump. If that has been missed, it could be clogged and starving you for fuel.
And my favorite other easy thing to look at, that I did about two years ago, is make sure you have not hit the emergency shut off switch in the engine bay. The engine will turnover, but not start. (I hit mine when I was leaning in the back door with a flashlight getting the fan belt part number. Took me an hour of sweating bullets before I thought about looking at that switch... I had bumped it.)
Other then that, follow the wires to Lift Pump, and disconnect and connect them, to see if it might clean up some gunk build up preventing full current.
And, I hope someone else with your coach or chassis, can help you with the fuse location, I would guest back in fuse box close to where the main rear power off switch is - but admit I don't know if your chassis has the same layout as mine.
Best of luck, and please let us know what you find out,