Here's a link
to the battery diagram for your coach. You want to look at sheet 4 of the PDF document. It shows two batteries. On this drawing the negative terminals of the batteries are to the left, and the positive to the right. The negative post on the left battery has two cables attached to it (black and black). The positive post of the right battery has two cables attached to it (red and yellow).
1) the batteries are oriented in the tray correctly, and
2) the cables are attached to the correct posts, and
3) the post connections on the batteries are clean and tight
Report back on your results.