ruuvitag GATT services

Actually that error you pointed to is for ESP32 - I don't believe it was ever an issue on official boards.

Thanks @Robin - there's a good example of using UUIDs at the link you posted on http://forum.espruino.com/conversations/323285/

And actually looking again at your code it's obvious - sorry I didn't spot it before! You're actually trying to use the text 'serviceUUID' itself as the UUID, not '6e400001b5a3f393e0a9e50e24dcca9e' :)

// for instance these two are identical:
print({
    serviceUUID : {
      characteristicUUID : {
     }
  }
});
print({
    "serviceUUID" : {
      "characteristicUUID" : {
     }
  }
});
// what you want is
print({
    '6e400001b5a3f393e0a9e50e24dcca9e' : {
      '6e400003b5a3f393e0a9e50e24dcca9e' : {
     }
  }
});

If you want to use the UUIDs as constants at the start of the code you'd have to manually set it in code:

var services = {};
services[serviceUUID] = {};
services[serviceUUID][characteristicUUID] = { ... };
NRF.setServices(services);