Hi @ababatola ,
I hope you're doing well! Sorry for the late reply.
I'd recommend taking a look at the rpmsg_lite_str_echo_rtos multicore example found in the i.MX 8M Plus SDK. It's a simple application which allows you to send a message from the Cortex A to the Cortex M and then M4 displays what is received, and echoes back the same message as an acknowledgement.
You can build and download the SDK from https://mcuxpresso.nxp.com/
Let me know if this works for you.
Best regards,
Hector.