Yes I've tried that before, still no page.
But now it is fixed: 😄
I connected my Iphone to the duetAP, because I wanted to scan the open ports on the duet.
It found the port 80 open and when I opened in safari, I got the wifi-setup-page.
Really odd behaviour, because I've tried everything (clear dns cache, setup VM with clean windows, reset my tablet, even used a console browser…) nothing worked
I never had any problems with other esp8266.
Thanks anyway!