@JD1 Do you know how to setup your extender via internet browser?

@Ewelinam can you show us (print screens) from your setup and status tab from your extender?

@NickOne Are you verifying it at one device or more? Can you show us signal 5GHz band level at yours devices?

@Plomborg Plomborg wrote The question is. When being used as a Stationary Router, can it then be connected up to a Range Extender, so it can connect to it in all rooms. You can use wireless extender...

@Aravind_5g Do you have new device or not? Sorry but you have gave us too little information in this subject.

@arman_1397 Those are questions for TP-Link Support or firmware developers. Sorry I can't give you a satisfaction answer