@Vibi 

Hi, May I know who is your internet service provider and what is the model number of the cable modem?

When Deco turned red, if you go to Deco APP>More>Advanced>IPv4, is there any internet IP address here?

Have you ever connected a computer to the modem with cable directly to check whether the ISP modem might be the issue?

And when the connection lost, if not resetting the modem, would restarting the main Deco help or not?

Thank you.