@Fraidiecat 

Hi, Thank you very much for the feedback.

Please also try to power restart the ISP modem once if possible.

By the way, Can you still detect the WiFi network of Deco under WLAN settings on mobile devices?

- if yes, please try to connect to this WiFi and open the Deco APP again to see whether you can view the previous Mesh network.

- then you could go to Deco APP>More> Internet connection>IPV4 to check whether there is a valid IPV4 address.

If the Deco Network doesn't show up on the Deco APP even when connecting to the Deco WiFi, it is suggested to reset one of the satellites Deco P9, and then try to create a new Mesh Network with this unit.

How to Create a New Network in the Deco App

Wait for your reply and best regards.