I added the call inside loop() just to prove of the keypad and function were actually working, whih they are.
I'll have a frenzy look at it today. It was 4am when I gave up. LOL
I quickly tried switching back to the normal buttons and that didn't work either. When I switched to the original sketch, without Keypad in, it worked again. The only other differene is me changing the same menu structure from 'tree' to 'menu'.
It may be something else and I'll investigate further today and have another attempt at making it work, before I bring all this code into my main project.
Hopefully I can get it working and you can then use this as your custom keys example if you like. It would be good as it shows how to do it with a standard keypad using another library. That can easily expand to a user creating their own whole button hanging routine for something like analogue buttons.