It is definitely installed correctly. My question has more to do with the 7219 than Arduino/code. In your experience working with the 7219 when they fail, have you ever seen them just turn all LED segments on and lose the ability to interpret the Din? Or do they tend to just shut down all together and do nothing?
My comment about the soldering temp related to the Maxim 7219 datasheet that specifies 300C maximum temp for 10 sec, and I was under that temp during install. Is it possible that it burned up? Sure. Is what I'm observing evidence of that, or a bad chip?
Thank you for your thoughts,
Robert