Could be many things really. As JimM68 said. The engine batteries will be bigger in size and 12 volt (I dont know if your Vectra had 1 or 2 engine batteries) Likely 2. They should be connected pos to pos and neg to neg. The coach batteries could be several 6 volt, or a couple 12 volt. If 2 12 volt, then they are also pos to pos and neg to neg. HOWEVER, if they are a few 6 volt, then they wire pos to neg, and neg to pos, ETC. (ALWAYS TAKE A PICTURE OF YOUR BATTERIES AND WIRING BEFORE REMOVING THEM)
Now there is a breaker near the batteries somewhere that could have thrown. (It does not look like a typical breaker) but more like a little black box with a small reset button "generally" on the bottom. Also, find your "battery disconnect" switch. If that is off. You wont have any 12 volt working.
Now if you wired everything up right, and your reset is not tripped, and your disconnect switch is "on". Does your engine start? If so, maybe your coach batteries are simply dead.
If all is good and your engine starts, Then (while your engine is running) press and hold your "battery boost" or "emergency start" button, and start the generator. (OR) use jumper cables from engine to coach batteries. Remember the Generator starts from the coach batteries. The Emergency start button literally ties coach and chassis batteries together.
