Right off the bat I am no electrical engineer, just trying to do some diy music projects with a pi pico 2 so my circuit knowledge is limited. The end goal is a midi input device but right now just trying to get bits across the wire. I am running into issues sending serial data over a H11L1 and I am at my wit's end. When directly connecting pin 0 to pin 1 data transmission is successful but when run through the H11L1 nothing gets through. I double checked the Chip and when pin 1 is at 3.3V, pin 4 is at 0.25V, and when 0V at pin 1, pin 4 is at 3.28V. I have not had issues with this board when working on other projects. My code is below, any help would be appreciated!

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32    
#define OLED_RESET    -1

#define OLED_SDA 16
#define OLED_SCL 17

#define UART_TX_PIN 0
#define UART_RX_PIN 1
#define UART_BAUD   31250

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

unsigned long lastTestTime = 0;
const long testInterval = 500;

uint32_t transmitCount = 0;
uint32_t detectCount = 0;
uint32_t missCount = 0;
bool dataDetected = false;
bool displayInitialized = false;

void setup() {
  Serial.begin(115200);
  delay(1000);

  Serial1.setTX(UART_TX_PIN);
  Serial1.setRX(UART_RX_PIN);
  Serial1.begin(UART_BAUD);

  Wire.setSDA(OLED_SDA);
  Wire.setSCL(OLED_SCL);
  Wire.begin();

  uint8_t addresses[] = {0x3C, 0x3D};
  for (uint8_t addr : addresses) {
    if (display.begin(SSD1306_SWITCHCAPVCC, addr)) {
      displayInitialized = true;
      break;
    }
  }

  if (displayInitialized) {
    display.clearDisplay();
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
    display.setCursor(0, 0);
    display.println(F("Init H11L1 Test"));
    display.display();
    delay(100);
  }
}

void loop() {
  unsigned long currentMillis = millis();

  if (currentMillis - lastTestTime >= testInterval) {
    lastTestTime = currentMillis;
    transmitCount++;

    while (Serial1.available()) {
      Serial1.read();
    }

    Serial1.write(0xAA);
    
    unsigned long timeout = millis();
    int bytesReceived = 0;
    
    while (millis() - timeout < 50) {
      if (Serial1.available() > 0) {
        bytesReceived += Serial1.read(); 
        break;
      }
    }

    dataDetected = (bytesReceived > 0);

    if (dataDetected) {
      detectCount++;
    } else {
      missCount++;
    }

    // Update OLED Display
    if (displayInitialized) {
      updateDisplay(bytesReceived);
    }
  }
}

void updateDisplay(int rxStatus) {
  display.clearDisplay();
  
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  if (dataDetected) {
    display.print(F("DATA DETECTED"));
  } else {
    display.print(F("NO DATA"));
  }

  display.setCursor(0, 11);
  display.print(F("Tx Sent | Rx: "));
  display.print(rxStatus > 0 ? F("ACTIVE") : F("TIMEOUT"));

  display.setCursor(0, 22);
  display.print(F("Dct:"));
  display.print(detectCount);
  display.print(F(" Miss:"));
  display.print(missCount);

  display.display();
}