Hi and welcome to the community!
Are you sure the device is sending CAN data periodically?
Sometimes, you have to query the remote device to receive a response in the CAN bus.
When I had to debug my code, I bought a CAN bus J1939 simulator, like this one:
I talk a bit more about it in this topic.
Or you can use the CAN simulator that Particle has created, it helped me in my CAN adventures incredibly.
It’s in a zip file in the Simulator folder, and it is referenced here:
Edit: here’s a pic of the photon-based simulator:
