Bag created with rosbag api is not publishing

I am new to ROS. I am attempting to take pointcloud data that is in a format not compatible with ROS and convert it to a ROS bag using the C++ rosbag API. I am having an issue with the newly created bag not publishing data to the topic. For example, whenever I use the command "rostopic echo my_topic" while playing the bag with "rosbag play newConverted.bag" there is nothing printed to the console. If I open the newConverted.bag with rqt_bag, right click on a topic and select publish, the data is then published to the topic and I can see it in rviz and with the rosbag echo command as expected. I must be missing something in my bag conversion code that tells ROS to automatically publish the topic when playing. Thoughts?