My grandmother had the same problem once - there was the problem that cables were mixed up in the distributor. A technician solved the problem a few days later.
In my case the problem was that something was wrong with the firmware - I called the support and asked. The lady then helped me to solve the problem by completely flattening the software on the router and then reinstalling it.
I would also recommend you to call the hotline at 0800 800 800 and ask. If they don't find anything, they may be able to make a test replacement or send a technician.