Notebook can produce no (WLAN) connection to the Fritzbox 7490 - why?

We switched to fiber optics (directly from the German fiber optics) and I try to install the extra Fritzbox 7490.

My notebook also recognizes this in the WLAN, but can't connect. Also via LAN cable unfortunately unsuccessful. On my son's laptop, the wireless connection was right there and I could enter the network key. Unfortunately, I did not continue with the facility there; sorry woman and technology ;-)

What could be the problem? I use Windows 8.1; Internet Explorer 11

Is DHCP active in the Internet protocol of the computer?
This is probably related to the TCP7IP of the computer.

How to enable DHCP or change other TCP / IP settings (here in Windows 10)

Select Start (WindowSysmbol at the bottom left corner of the screen), then Settings> Network and Internet or Change Adapter Options> Wi-Fi.
Select Manage known networks. Select the network for which you want to change the settings, and then select Properties.
Under IP Assignment, select Edit.
Under Edit IP Settings, select Automatic (DHCP) or Manual.

If you select Automatic (DHCP), the IP address settings and the DNS server address are automatically set by your router, ie the Fritzbox or another access point (recommended).

Otherwise, please enable Google with the keywords "DHCP Windows 8.1". Because unfortunately I have WINDOWS 10 and therefore not the exact menu items on the screen.