Just noticed the power link in the hall is not flashing green as per usual. The one upstairs is fine. Consequently, I can't get on the internet in my normal fashion. Now on via Wi-Fi. (bt internet). Am I correct in thinking the one down stairs is broken? I have had them about 4 years. How can one test them? They are ZyXEL HD . Should I just purchase 2 more. The were about £40 so they don't owe me anything. Thanks. Which are the best one?