As Mark said, you need a wire from the new batteries to your DC buss bar to get 12V power to your rv. In the case of my upgrade, this connection was previously made by a short jumper wire at the coach battery connection to the battery isolator (which was near the rear buss bar - not under the hood).
Since I was no longer using the original battery isolator in favor of a new DC to DC with lithium charge profile, it is now just sitting there disconnected. So I ran ran a new 4 gauge wire with an in-line ANL 40A fuse (or is it 60A?) from the lithium batteries to the power bar. Problem solved.
Don't know if yours looks anything like mine, but here is a picture of my prior jumper connection that I ran the new 4ga. wire to replace.