Hi,
the issue could be anywhere. Program could be OK (I are absolutely sure there a re no changes) but the system you have put your node into could be different - I do not know, you have not described.
If I were in your shoes I would:
1) check the bus clock and/or oscillator clock to be sure the CAN clock is OK. Also check all the nodes connected to the bus use the same you are connection to
2) test the CAN in the loopback mode to be sure CAN peripheral is OK.
3) test the communication between two CAN nodes at the same MCU without transceiver to be sure the communication is OK. The circuit can be found https://www.mikrocontroller.net/attachment/28831/siemens_AP2921.pdf
In this case I would also measure the CAN signal by the scope whether the communication speed is OK.
4) If the everything above is OK then the issue is on the transceiver side and/or BUS.
I know, it is easy to write it but difficult to test. However, it is necessary to go step by step to exclude possible sources of issues.
Best regards,
Ladislav
