@TP-Link  can you please advise what to do here?

@TP-Link The client devices are connecting to the Deco's themselves - the Deco's however are not letting the client devices see the Internet. The error message is essentially "No internet connection" - many other devices are connected to the Internet through the Deco's and all of these devices were until recently!  The devices are all already on WPA2-PSK. I will try turning off 5ghz on the main network. As per other suggestions on the forum I had already tried connecting the devices to the Guest network with the 5ghz turned off - which did not work. I think I will need to send you a private message of the MAC address of the main Deco and the TP-Link email ID for Deco APP. I am however unsure how to do this through this platform?  Thanks Jamie

@TP-Link also I have tried restarting all of the client devices themselves, modem and X20 devices - no change still could not connect to Internet.