How to create custom service and characteristics

Is the issue just that you're still connected to the Puck with one device? It can only accept one connection at a time so won't even advertise while it's connected. If you want to debug things you can always wire up a serial connection (details on the Puck.js page).

I think 00001801-0000-1000-8000-00805f9b34fb (which is actually just a 16 bit UUID 1801) is a standard Bluetooth way of flagging up when the services advertised by a device have changed.

Other things that might help:

• I'm not sure, but using 00000... as the UUID could be causing problems - it's extremely likely it's reserved (it's not a 16 bit UUID if that's what you had intended). I'd either use a normal 16 bit UUID, or use a totally random 128 bit UUID as a base and just vary the 16 bits in the middle like you do currently.
  
• The Nordic devices can't change the services that they advertise on the fly, so Espruino has to actually restart the whole Bluetooth stack if items (like UART) are to be removed - hence the message. Obviously if it does that it'll disconnect any connected devices, so it waits until you disconnect. If you just want to update the content data in services then just use NRF.updateServices