Serial Print makes code work. Why?

Projects Programming
9

OK seems the Adafruit_GFX_Library expects modifiable data. I'm not sure they modify it and it's likely a mistake from them not to have declared the parameter as const, but that's what is there...

so go for either

char *titleStr[row * col] = {"4", "6", "8", "9", "12", "16", "Load", "1", nullptr, nullptr, nullptr, nullptr};`

Or (wasting memory)

char *titleStr[row * col] = {"4", "6", "8", "9", "12", "16", "Load", "1", "x", "xx", "xxx", "xxxx"};