I'm trying to add a watchdog on an Arduino Nano, for my code, and I'm following the code in [this manual][1] exactly, but after the amount of time for not resetting the watchdog, it resets but does not reboot.

In the last paragraph it says that:

> However, I could not find something similar in Optiboot bootloader (If
> I'm wrong, correct me please!), used by Arduino UNO and other new
> boards. It seems that they sacrificed this check for size. So, it is
> possible that watchdog timer will be enabled after reset, so -  if you
> set it's value too low, your board may never come out of bootloader
> stage. So, to be always on the safe side, set watchdog to longer
> periods (2S and more).

So I've tried for 8 s, but still same result.

What is wrong?

    #include <avr/wdt.h>
    int k=1;
    
    void setup() {
      Serial.begin(9600);
      wdt_enable(WDTO_8S);
    }
    
    void loop() {
      //do stuff here
      k++;
      wdt_reset();
      Serial.println(1000 * k);
      delay(1000 * k);
    }

  [1]: https://tushev.org/articles/arduino/5/arduino-and-watchdog-timer