Why is my Callback function not called?

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Hello,

so I have the following code:

These are my callback functions:

void callbackVel( const cu_msgs::CAN_VCUStateEstimation::ConstPtr& msg ) {
    ROS_INFO("HELLO");
    speed0 = msg->velocity[0] < 0.1;
}

void callbackPose( const geometry_msgs::PointStamped::ConstPtr& msg) {
    Vector3f tmp = vehiclePose;
    vehiclePose = Vector3f(
        msg->point.x,
        msg->point.y,
        msg->point.z
    );

    //increase driven distance
    odometer += (vehiclePose - tmp).norm();
}

And these are the subscriber definitions:

    ros::Subscriber subVel = nh.subscribe< cu_msgs::CAN_VCUStateEstimation >("/mailman/state_estimation", 1, callbackVel);
    ros::Subscriber subPose = nh.subscribe< geometry_msgs::PointStamped >("slam/best_guess/position", 1, callbackPose);
   ros::Rate r(10);
   while (ros::ok()) {
        //do stuff
        ros::spinOnce();
        r.sleep();
    }

The callback function "callbackPose" is called regularly as it should, but the callback function callbackVel is never called. Even though when I listen to "rostopic echo /mailman/state_estimation" I get the message at a frequency of about 100Hz. What could be the reason for that?