problem with Hardware Serial

I have plugged the Movi Shield to the top of Arduino mega and it works fine
then I wanted to connect Arduino Mega to another Arduino Uno by Serial hardware
so I connected the Pin TX314(Mega) to RX(UNO) and Pin RX315(Mega) to TX(UNO) and Ground From Mega to Ground From UNO, and also J1 is Open, J2 and J3 are closed
and I used this Code :
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MOVI recognizer(true,&Serial3);
void setup() {
Serial3.begin(9600);
recognizer.init();
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there is a conflict between Serial3.begin(9600) and recognizer.init() does not work together
I have to delete one of them so the other command will start working
please help me and what I have to do?

That’s effectively what I do and my sketch works fine. What do you mean by “does not work together”? Does your sketch hang or…? Need symptoms to consider giving advise.

I have a similar situation. Except I lose SERIAL MONITOR and SERIAL3.

Everything runs, but the connection on Serial3 is to a ESP32 for network activity.