You might need to reset the modem. To do that you just unplug the modem and leave it unplugged for a minute or two then plug it back in. Let it connect then try and access the Internet again after a few minutes.
If that still doesn't work, you probably need to call your DSL provider.
Hope this helps (when our Internet is slow or my devices can't "find" the Internet - this is how I fix it)
If the DSL on your internet is not working, try to turn your DSL modem off for about one minute and if it has battery backup, you will need to remove the battery. This process helps your modem reboot itself. You can also restart your computer if it has been on for a long time. Lastly check your cables to make sure they are intact.