@JawadTP Glad to hear you made it work. Who knows, maybe you powerline adapters set needed gentle push to start working with Deco, and PC provided that push. Maybe CCTV only decided to renew IP...

@1Steven Wiring Cisco 8865 VOIP to Deco helps to eliminate possible issues, and also if that works - provides a solution without need for more troubleshooting. You can't bring two close together to...

@1Steven Cisco 8865 VOIP phone specs say it supports gigabit Ethernet connection. Wire it to Main or to Satellite Deco by Ethernet cable.

@JawadTP It is possible that your CCTV system is configured with static IP address, which is no longer valid because you now have Deco providing IP addresses from the different IP range. If you have...

@Mike-Chen There could be settings in Deco responsible for throttling traffic, but other scenario also possible: Deco pushes your device to slower 2.4GHz or Main Deco negotiated 100Mbps wired link...

MedMez wrote @Alexandre. After trying without success to get a x series deco, I tried directly your suggestion 2, switched all decos to access points and used my original Huawei provider router......