Hi,
Hope you are doing well. In the readme.txt of the example you can see that "the example will send a CAN Message from the Tx Message Buffer to the Rx Message Buffer throuth internal loopback interconnect". The example shows how to use the loopback test mode to debug the CAN Bus design.
Can you check the flexcan_interrupt_transfer example? In this example, 2 boards are connected through CAN bus. You can find the Board settings in the readme.txt. And don't forget the 12V power supply on J32.
Best Regards,
Ricardo