rgbdx_sync node is not found, which version are you using?
Example
rosrun rtabmap_ros rgbdx_sync
[ INFO] [1662428278.088920840]: Initializing nodelet with 12 worker threads.
[ INFO] [1662428281.072218579]: /rgbdx_sync: approx_sync = true
[ INFO] [1662428281.072342629]: /rgbdx_sync: approx_sync_max_interval = 0.000000
[ INFO] [1662428281.072368785]: /rgbdx_sync: queue_size = 10
[ INFO] [1662428281.072391304]: /rgbdx_sync: rgbd_cameras = 2
[ INFO] [1662428281.080020952]:
/rgbdx_sync subscribed to (approx sync):
/rgbd_image0 \
/rgbd_image1