Seeed Xiao won't work with Uctronics SSD1306

I have purchased a couple of SSD1306 OLED displays (128x64), which run on 3.3-5V and the I2C bus; with my Arduino Uno R3 I can get the OLED working (I’m using the example code provided in the Arduino IDE).

The Xiao will not work with the SSD1306 displays and the example code.

There are only 4 pins; 5V, GND, and SDA,SCK. The I2C address is 0x3C.

Any tips/info would be appreciated. Such a simple setup that I can’t imagine why it will not work.

Pull up resister are needed I2C SDA and SCK signals.
Same device have that by self.
But usually have not. These are data rate independent.
Data rate is around 100k. You can use about 1k to 10k ohm resister.
You should be check line state by DSO or like that.
If you can not check line. you should be better to buy shield things.

Thank you for this info. I blanked on the pullup resistors for the bus lines. I will put a scope on this weekend.