robot_pose_ekf won't publish any messages

Question

I am having trouble getting the robot_pose_ekf package to publish messages. I launch it with this launch file.

<launch>

  <!-- Extended Kalman Filter from robot_pose_ekf Node-->
  <!-- Subscribe: /odom, /imu/data, /vo -->
  <!-- Publish: /robot_pose_ekf/odom_combined -->

  <remap from="/imu_data" to="/imu/data" />

  <node pkg="robot_pose_ekf" type="robot_pose_ekf" name="robot_pose_ekf">
    <param name="output_frame" value="odom"/>
    <param name="base_footprint_frame" value="base_footprint"/>
    <param name="freq" value="30.0"/>
    <param name="sensor_timeout" value="1.0"/>
    <param name="odom_used" value="true"/>
    <param name="imu_used" value="true"/>
    <param name="vo_used" value="false"/>
    <param name="gps_used" value="false"/>
    <param name="debug" value="true"/>
    <param name="self_diagnose" value="true"/>
  </node>

</launch>

But then I get lots of these errors:

[ WARN] [1636570848.059506230]: MSG to TF: Quaternion Not Properly Normalized
[ERROR] [1636570848.059787913]: Covariance specified for measurement on topic imu is zero
[ERROR] [1636570848.060134410]: filter time older than odom message buffer
[ WARN] [1636570848.074015563]: MSG to TF: Quaternion Not Properly Normalized
[ERROR] [1636570848.074583539]: Covariance specified for measurement on topic imu is zero
[ERROR] [1636570848.085433183]: Covariance specified for measurement on topic wheelodom is zero

And I get this output from wtf, which says I'm getting inputs but am not publishing any messages on topic /robot_pose_ekf/odom_combined.

doug@raspi4:~$ rosrun robot_pose_ekf wtf.py looking for node robot_pose_ekf... Input:

• Odometry sensor
  • is used
  • is active
  • received 12 messages
  • listens to topic /odom
• IMU sensor
  • is used
  • is active
  • received 152 messages
  • listens to topic /imu/data
• Visual Odometry sensor
  • is NOT used
  • is NOT active
  • received 0 messages
  • listens to topic
• GPS sensor
  • is NOT used
  • is NOT active
  • received 0 messages
  • listens to topic Output:
• Robot pose ekf filter
  • is active
  • sent 0 messages
  • publishes on topics /robot_pose_ekf/odom_combined and /tf

My IMU data is coming from a BNO055 device publishing with code from https://github.com/RoboticArts/ros_imu_bno055.

Any ideas what might be going on?