Do we know where to find security key?

No, I do not know, it is why I am asking.

There are more knowledgeable folks here, so hopefully this is helpful and, if not, someone will correct me.

Although it’s not always the case, I think in this instance, “network security key” probably just means password.

So, if you are just setting up the gateway, it’s one of the keys/passwords on the label on the bottom of the unit.

If the unit is already setup, it should be the wi-fi password you created then. However, if you’re trying to connect the T-mobile Internet app to the gateway it would be the administrator password that was created when you did the setup. I think the two passwords (wi-fi and administrator) can be the same, but it’s usually best if they’re different.

@syaoran  any ideas on this one?

I always recommend factory resetting those and using the app to set them up from scratch.  That way, you go through everything without guessing what happened to it with the person who potentially had it before.

Thank you Darko66 your advice worked like a charm

Where do I find the network security key?

 Thanks 

Thank you! It worked! You’re the best!!!