Is clock to the CAN module enabled? Check for this if writes to CAN registers are not going through. Clock is enabled through a bit in the PCLKCRn register.
Comment all EDIS from your code until you get it to work. You could add it later. Many registers and bits are EALLOW protected and a write may not go through if EALLOW is not active.
Try your code without interrupts first. Use polling instead. Once polling works, you can add interrupts later.
If a specific mailbox is not working, have you attempted to use a different mailbox? Have the mailboxes been enabled and the mailbox direction correctly configured?
When attempting to initiate communication on the bus for the very first time, ensure that the the mailbox in the transmitting node and the receiving node are programmed with the same MSGID. Do not use Acceptance Mask Filtering initially. Filtering could be added later once it is confirmed there are no hardware issues with the bus.