Hi,
as the warning says, did you try:
$ rostopic hz /rtabmap/odom
$ rostopic hz /camera/rgb/image_rect_color
$ rostopic hz /camera/depth/image_rect_color
$ rostopic hz /camera/rgb/camera_info
to see if all topics are actually published? If not, the problem is thus why they are not published (maybe wrong topic name).
cheers,
Mathieu