I have an Arduino R4 Minima and a Gravity: 4-Digital LED Segment Display Module (Red) SKU: SKU: DFR0645-R

In my testing so far, the display is always black.

I have downloaded and run the ledFlash and ledPrint examples from here https://github.com/DFRobot/DFRobot_LedDisplayModule/tree/master/examples as well as the examples that come with the HT16K33 library for Arduino.

I have checked my wiring carefully and have verified that power is getting to the display by probing the solder pads where the connector attaches to the back of the display with my DMM. I see power on the SDA and SCL lines occasionally as well. So I think there is a good electrical connection on all 4 lines.

I have tried I2C addresses 0x48, 0xE0, 0x70, 0x7E as I have seen each of these mentioned in various pieces of sample code.

Any ideas on what might be wrong?

The Arduino is known to generally work, but the I2C has never been used before.

The display is new, so it is possible it is defective, but that seems very unlikely.