Can´t activate and link my USG20 license at MyZyxel

Problem:

I want to activate a license for my USG20 on portal.myzyxel.com.
When i try to link it a popup says no compatible device.

What went wrong?

Answer:

There are different USG20 models.

USG20W-VPN
USG20W
USG20-VPN

Please take special care that you order the correct license before buying and activating them at MyZyxel!

KB-00201