Nexus 10 Wi-Fi problem :(

Hello

I have a Nexus 10 and a FritzBox 7360SL.

I was last week in Belgien now i´m back @home and now i cant connect my Nexus 10 with the FitzBox.
The same Problem i have with my SmartPhone Xperia Z3. there is some kind of a sign on the Wi-Fi connection (exclamation mark).

I reset my FritzBox back to Factory but nothing helps.
I also reset my Nexus 10 the problem is still there.

I hope you can help me.

Thanks