Funny you mention the QSS button but I had a similar experience with a TP-Link wireless hub I was using as an extender. Slaved away for hours trying to get it working by manually configuring the device with NO LUCK.
Buried away in the manual was a not very well written section about QSS. So all I had to do was pick from a menu how I wanted the device to function and then hit the QSS button. I was 100% convinced it wouldn't work but it did and has carried on working day-after-day!!!!

