No DSL connection

Hello everyone.

I have been away for a couple of days and have turned my router off. After I came back and turned it on again, the DSL light stays off. I have the o2 box (no fritzbox). The manual says that when the DSL light is off there is a problem with dsl connection.

I have reset the router multiple times in multiple ways just to rule that out. I always get stable wifi, but no internet access. This leads me to think there is some hardware problem either with the router or that someone has disconnected my wires from the Telekom socket. I have no idea how to check that. I would really appreciate some help on fixing the internet access. Thanks.