Using the built in serial connection

Hello! I am trying to build a Bluetooth media controller to connect to my phone while in the car and have buttons for skip, volume, etc...
I am having trouble getting the internal serial connection between the two boards working. I tried on my own, and am now getting help from the google AI chat thing, with the same results. I'll post the code here, what am I doing wrong?

I have very limited knowledge of programming these things, I'm just finding sample code from other places and pasting in what I think will work. Yes I know there's an rp2 w, but I don't have one of those and do have one of these from when it was like $9.

for the rp2040

Code:

#include <Arduino.h>

const int ledPin = 25; // LED pin
const int buttonPin = 27; // Pushbutton pin
const int baudRate = 9600; // Match ESP32 baud rate

int ledState = LOW; // Initial LED state (off)
bool buttonPressed = false; // Flag to track button press

void setup() {
  Serial.begin(baudRate); // Default serial for communication
  pinMode(ledPin, OUTPUT); // Set LED pin as output
  pinMode(buttonPin, INPUT_PULLUP); // Set button pin as input with pull-up resistor
}

void loop() {
  // Check for button press (active low with pull-up)
  buttonPressed = !digitalRead(buttonPin);
  if (buttonPressed && !digitalRead(buttonPin)) { // Debounce (check twice for stable press)
    String message = "RP2040: Toggle LED"; // Message with identifier
    Serial.println(message); // Send message to ESP32
    ledState = !ledState; // Toggle LED state
    digitalWrite(ledPin, ledState); // Update LED
    delay(100); // Short delay to debounce button further (optional)
  }
}

ESP32

Code:

const int ledPin = 32; // Blue LED pin
const int baudRate = 9600; // Adjust if needed

int ledState = LOW; // Initial LED state (off)

void setup() {
  Serial.begin(baudRate); // Default serial for communication with your computer (optional)
  pinMode(ledPin, OUTPUT); // Set LED pin as output
}

void loop() {
  if (Serial.available()) {
    String message = Serial.readStringUntil('\n');
    Serial.println(message); // Print received message for debugging (optional)
    ledState = !ledState; // Toggle LED state
    digitalWrite(ledPin, ledState); // Update LED
  }
}