I am currently working with mqx 4.1.1 in IAR and having issues with flexcan transmission. I am using the RxFIFO and I have one mailbox configured for transmission. Every so often I notice that the data gets put in the mailbox and the code changes to data (0x0C) but then the message just sits there, no interrupt is ever exerted to signal a valid transmission. Pausing operation to look at the registers doesn't show any errors and that the message buffer is still set to Data and the iflag is clear. However receiving another message on the inbound RxFIFO seems to kick the system and the message in the buffer will then be sent. I have a CAN Monitor on the system and can verify that the data never hits the wire. I have tried to setup multiple mailboxes and it still gives me the same results. Any help is appreciated.