Puck2.js Master/Slave: probem (red LED) when establishing the connection

I have the pucks named "c123" (master), and "ae23" (slave).
I followed the description at https://www.espruino.com/Puck.js+Controlling+Other+Pucks
1) slave: code copied to puck named "ae23" and save()
2) master: puck name changed to "...filters: [{ name: 'Puck.js c123'..." , code copied and save()

Testing with and without loading "require("ble_simple_uart")" on WEB IDE via "Send to Espruino"

The result is always
a) master: the blue LED is on (OK), then the red LED is on (KO)
b) slave does nothing

What do I do wrong?
Thanks for the answer!

It sounds like you've got the master/central "c123" (the one doing the connecting) trying to connect to itself with ...filters: [{ name: 'Puck.js c123'...?

I think you need: ...filters: [{ name: 'Puck.js ae23' instead and you should be ok?

oh, sorry, my copy/paste was wrong here :-(
here is the test what I made, and I have the problem in this version:

//===========================================================================================================================================
Slave:

var on = 0;
function toggle() {
  on = !on;
  digitalWrite(LED, on);
}

--> save();

//===========================================================================================================================================
Master:

// Are we busy?
var busy = false;

// Function to call 'toggle' on the other Puck
function sendToggle() {
  if (!busy) {
    busy = true;
    digitalPulse(LED3, 1, 500); // light blue to show we're working
    NRF.requestDevice({ filters: [{ name: 'Puck.js ae23' }] }).then(function(device) {
      require("ble_simple_uart").write(device, "toggle()\n", function() {
        digitalPulse(LED2, 1, 500); // light green to show it worked
        busy = false;
      });
    }).catch(function() {
      digitalPulse(LED1, 1, 500); // light red if we had a problem
      busy = false;
    });
  }
}

// Call sendToggle when the button is pressed
setWatch(sendToggle, BTN, { edge:"rising", debounce:50, repeat: true });

--> save();

Is it possible that you're still connected to the slave device with your PC?

Espruino BLE devices can only have one device connected to them at a time, so if you're connected with your PC, the 'master' device won't be able to connect.

Also, if you stay connected with the 'master' you could change the code to:

    }).catch(function(e) {
      digitalPulse(LED1, 1, 500); // light red if we had a problem
      console.log("Error",e);
      busy = false;
    });

And you might be able to see what error it is complaining about

Thank you Gordon, it's working now!
I think the require("ble_simple_uart")" on WEB IDE via "Send to Espruino" was not correctly executed - it runs now fine.

I tried now also the 2nd example ( at "Making it faster" ):
Here I have the following problem:
1) I press the button on master-puck, the green LED lights; now the red LED lights also on the slave-puck(this is OK);
2) if I press the master-puck again, the red LED is OFF on slave-puck (this is OK also);
3) I play this 3 times (on and off)
4) After the 7. button press on master-puck, the green LED is always lights on master-puck, but the slave-puck do nothing. Only if I make a reset() and a new load/code copie to the master can I run this procedure again.
5) .. and I cannot connect anymore to my slave-puck via WEB IDE, I must remove/put in again the battery

What could be the problem here?

I just found: if I re-insert the batteries after the 4) step above (without re-loading the codes), then everything work correctly. So I think it's not a problem anymore.
Thanks!