Why is my Keypad not working with 5x5?

[6v6gt]

What board are you using?
You could try the code in post #16 here to help isolate the problem:

Picking up stray voltage when handling 4+4 matrix keypad. What could be wrong?

I’m glad that worked for you. Now that you have pointed out the issue related to the Teensy 4.1, I’ll restructure the code to do the INPUT_PULLUP settings as early as possible so they have a chance to be fully active before the corresponding digitalRead() statements are called. That will minimize the need for delay() statements in code. It will, however, add two for loops. If I then notice that other users have similar problems, I’ll refer to this thread. Restructure to increase the interval …