Greetings there,
 

I just bought 2 new TP-Link routers - the Archer C50 and the C20 - for me and my girlfriend and I have the exact same problem - tested both routers in both apartments;

I have no internet at all - internet icon is NOT lit (not orange, not yellow, nothing), it just blinks orange for half a second when I power the router up and then nothing. All the other icons are properly lit.

Now, before you say anything,
a) I've connected the routers straight to the wall (no other routers or modems in between).
b) All of my past routers went straight to the wall and worked the moment I connected the cables and turned them on.

c) All of my devices (either wireless laptops or wired desktops) are properly connecting to the routers, so there's no problem there, the problem is that apparently it does not detect (?) the phone signal?
d) As you may guess, I try to do the quick setup but it won't let me past the second step as it gives me a WAN cable unplugged error.

e) Also reset both of them.

As soon as I put my old routers back online, they connect to the internet without any issue. I would think there's something wrong with my phone line, but since it's happening to both routers in both apartments, I don't even know how to troubleshoot them.

Am I missing something obvious?
Thanks in advance

Edit: Ugh... Scratch that. I did not realize that having a modem is *required*. I guess it's a waste of money, since now I'm gonna have to use it along my old router in order for it to work.

And since we are on the topic, can someone explain the advantages of having a TP-Link router-only connected to an old modem, as opposed to a single TP-link router/modem device?
In order to take advantage of its features and connection stability, I guess even the old modem has to be high quality and not a cheap one?