I am sorry, I still do not understand your configuration.
The Arduino Mega is plugged into your computer's USB (that is Serial).
You have a MAX233 plugged into RX1, TX1 (Serial1). So you generate RS-232 level communication with the chip and that is plugged where? What is connected on the other side of the MAX233?
MAX233 chip which works fine because when I run the monitor I can see what the Arduino Mega is sending out(Serial.println)
Which monitor? The Arduino IDE's? Doesn't it only work with RX,TX and Serial? Do you mean you are echoing something like:
Serial.print(Seria1.read());
So how are you sending data to Serial1?