I can't get the Mega to receive the char I send.
And yet you failed to post the code that sends the data or the code that receives the data. I assumed that you wanted help. I must have assumed incorrectly.
The port and everything is ok.
If EVERYTHING was OK, you wouldn't have a problem. So, clearly, this statement is nonsense.
Can you please tell me how you fixed it?
OP used his brain.