@Iwao This may sound silly, but are you sure this "network client" connects to Deco mesh and not somewhere else? If it connects by WiFi, you should check that. --------------- This is just a theory,...

JohnJohn25 wrote Thanks for the feedback, but my router does not allow me to change my DNS server. It's blocked. Is there other way I can do this on the Deco? @JohnJohn25 Only by switching Deco mesh...

@yusufbogatepe In your case, this may help: Deco S7 1.5.0 Supports Connection Preference, IOT Network, WPA3 and More

@JohnJohn25 With Deco mesh running in AP mode you will have to set custom DNS on router to which Main Deco is connected.

@Antoine_B As I thought. It appears to be common issue among long term owners of Deco M9 Plus. For solution, see: https://community.tp-link.com/en/home/forum/topic/671334?replyId=1369784

@Antoine_B I saw this error message when not all Deco units in Deco mesh were updated to the version of firmware that supports Connection Preference feature. Make screenshot of Update Deco page from...