Arduino NANO watchdog issue

Hi

I have an issue due to the use of the watchdog on my Arduino NANO. The watchdog simply doesn't work as known from Arduino Mega and other of the Arduino boards I have programmed several times.

I have tried change the boot loader to "optiboot bootloader" without any luck. Many articles on the Internet says this boot loader will make the watchdog to be working...

Does anyone have suggestions to make the watchdog be working...?

Kind regards
Bjarke