@peter12345l
Hi, Have you checked when Deco was offline and turned red, can you still get an internet connection from the cable modem directly?
If not restarting Deco, could unplugging/plugging the internet cable between the main Deco X20 and modem restore the connection?
Or would restarting the modem restore the connection?
Could you please leave me a message about the IPV4 settings under Deco APP>More> Internet connection>IPV4 settings when Deco was red?
Please also refer to this link to change WAN DNS to 8.8.8.8/8.8.4.4 to see whether it helped:
How to change DNS server settings on my Deco
For more details, please also refer to Main Deco turned red light
Thank you very much and best regards.