Seeking help - Using CJMCU 8*8 LED matrix with arduino
I just received 2 of these from 2 different suppliers on EBAY.
None work using the pins called [GND +5V DIN]. As it turns out the DIN is actually NOT DIN. The other connector area [GND +5V DOUT] is the DIN. Ugh!

These boards are marked CJMCU-8*8 on the back side and on the front they say "WS2812B-64 RGB LEDS". Which is another issue. They are using the 6 pin WS2812, not the 4 pin WS2812B.

So if this is what your board looks like then perhaps try the pin marked DOUT for your DIN. Or try to psych out the traces to make sure first.