Iphones will not connnect to the range extender I have just purchased. It is an AX3000 Wi-Fi 6 Speed. The extender itself is working, as i am using it on this computer, but none of our Apple products will connect 2 x iPhones and 2 x iPads. The Firmware is up to date. If I put on the Airplane mode, I can see and connect to the wi-fi, but no data can be accessed and then the signal disappears. 

I have tried using the Tether App, then reset the extender before trying again. I have repeated this process using the WPS method and also tried plugging the extender into a couputer.

Any advice really appreciated. thank you