@Boyet 

Hi, I see that the Deco X20 kit is online again.

And I guess you have fixed your issue already?

If not, there are some suggestions:

1. Delete all the invalid old network names first on the APP.

2. Reset the main X20 by holding the bottom reset pinhole for 1s and follow the setup instructions on the APP.

3. Reset the rest of the other satellite X20s if their LED could not be blinking blue.

4. Since Deco X20 had a pre-configured program, normally we just need to wait for about 1mins, all the satellite X20s would be added to the APP automatically.

Thank you very much.