Only outputting zeroes with ESP32C3

[DragonNZ]

I am using 1.12.4, driving SK6812 leds.

The arduino program runs fine on the older ESP-WROOM that I have, but when running on the ESP32 C3, it just output zeroes in the data, no ones are sent.

I am checking this with scope, frequency is fine at 800KHz, but for some reason it's only sending zeroes to the LED strip.
I can see the ones when using the ESP-WROOM.

Any idea what may be going on?

My config is

//
// LED strip configuration
//
#define LEDS_PER_METER 60
#define LED_METERS 5
#define NUM_LEDS (LEDS_PER_METER * LED_METERS) // 5m x 60 = 300 addressable units
#define DATA_PIN 0

// Initialise the NeoPixel strip for an RGBW LED strip.
// NEO_GRBW indicates the colour ordering (Green, Red, Blue, White) and NEO_KHZ800 sets the data rate.
Adafruit_NeoPixel strip = Adafruit_NeoPixel(NUM_LEDS, DATA_PIN, NEO_GRBW + NEO_KHZ800);