Welcome to iRV2.
To me your post is fine .
Are there any systems in the coach or chassis that are not functioning ?
I ask , because the battery that's not connected could just be a second coach battery , that requires proper connections to the other coach battery to increase the power available for operating the interior 12 volt items in the coach when not using shore power.
Information on multiple battery hook ups ; both 6 and 12 volt are covered at this site below.
The 12volt Side of Life (Part 1)
But I'd want to have the battery tested before wiring it into the coach , there could be a good reason why it isn't hooked up.