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 three different USG20 models.

• ZyWall USG 20 [Old-Gen., Firmware 3.x (BDQ)]
• USG20-VPN [Next-Gen., Firmware 4.x (ABAQ)]
• USG20W-VPN [Next-Gen., Firmware 4.x (ABAR)]

Please take special care that you order the correct license before buying!

KB-00201