I do have one circuit hardwired that works perfectly ok. I am now constructing exactly the same circuit on a breadboard so I can eventually daisy chain the two together to scroll text effectively as a 16 x 8 matrix. The circuit on the breadboard is the problem one in so far as it works with one ( two character) code example (using your code with what I want displayed in showString) but another block of exactly the same code but with different characters in showString, briefly displays the first character of showString and the the display remains blank.