Why is showing invalid sim card

Hi @dz09

The DZ09 smartwatch only works with 2G (2nd generation) mobile phone networks.

If the SIM card that you're trying to use is from a mobile phone service provider that doesn't have a 2G network, it won't work.

2G is now becoming outdated and is being phased out most everywhere in the world.

If you scroll down the page in this link you can see in which country it might be still in use.

You could connect it via Bluetooth to a mobile phone and use it that way if you want to make calls etc, but then you need to have the phone on you or close by anyway as it can't be more than 10 metres away for the connection to be maintained, so there's no point in using it that way.