After few days of work I can no longer connect to my puck

No problem! If you need it, the connections are at http://www.espruino.com/Puck.js#serial-console

For the watchdog timer you just need http://www.espruino.com/Reference#l_E_enableWatchdog

So if you do E.enableWatchdog(2); then if Espruino crashes such that it's not executing anything in setInterval, it'll automatically reboot.

You can go one step further and manually poke it in your code, so you know that if your code doesn't execute that line in X seconds the device reboots:

E.enableWatchdog(1, false);                                                         
setInterval(function() {
  if (everything_ok)
    E.kickWatchdog();
}, 500);

You just need to watch out that if you go to update the firmware the watchdog will still be running and may cause a reboot if it isn't enabled in the new bit of code you update.

As I said above though, one reason you may not see it advertising is if some other device has automatically connected to it.

You could always add setWatch(()=>NRF.disconnect(),BTN,{repeat:true}) so when the button is pressed it disconnects from whatever it is connected to, and that might help?