Just a guess given the limited information. Maybe the antivirus suite expired. I'm running into this more and more where they block the internet when it expired.
Let me be clear. If I find such behavior I call it thuggish and advise removal of said suite and moving to another system.
I've been using a hotspot wifi with my Windows 7 computer for several months now. The hotspot requires login, the redirect is automatic. This morning I tried to connect and it says This site can’t be reached www.hotspots.de took too long to respond. I tried connecting with my phone, everything is working fine. I've tried connecting my computer to another (slower and weaker signal) hotspot which does not require login in, works fine. Help