I wrote a program to light up each LED one at a time by moving from row 0 to row 24 lighting up each LED in column 0 thru 24 for 5 seconds. Here is what I see...

. the LED in row 2 lights up continuously while that column is active
. the LED in row numbers 6, 10 and 14 thru 24 light up in order in the active column, the others never do light up; this is true for all columns from 0 to 24

I have checked that the parts are in the right place and that all ICs are seated properly. I can't see any solder bridges or cold joints. I'm guessing that the problem might be with U2, and the connections between it and U1, the processor. Please let me know if you have any hints to help troubleshoot this issue.

Did you configure your kit with the "Peggy 2 compatibility mode," or with the "Serial option"?

Peggy 2 compatibility mode

So, there are a few different possibilities. It would be helpful to separate potential software issues from hardware issues. Please try to load the "peggy2_minimal" sketch, and tell me what you see there.

It displays all LEDs and I recall the default peggy code displayed all LEDs as well. I believe that I just learned a valuable lesson. I was using Serial.begin and Serial.print as a debugging tool in my code and that apparently is a big no-no. Everything is good now. Thanks.

Great-- I'm glad that it's working.

If you need to use the serial options, I'd suggest reconfiguring with the serial option-- it should work fine in that case.