Note that the code in the Digital Hourglass example starts cycling above pin 7 after the hour is up, setting pins to low and essentially setting the pinMode(switchPin,INPUT_PULLUP), overriding the external pulldown, and making the button non-functional.

The code should either reset the hourglass automatically, or check that it is in the 2-7 range before setting the pin to low.

Maybe change the test to:

if (currentTime - previousTime > interval && led <= 7 ) {

Sped-up (6 seconds/step) Example:

https://wokwi.com/projects/422992836439284737