@Haziq try rebooting the whole system and restart then. If you still have issues contact support, I'm sure they know how to help

Plug the power cord for the modem back in, but leave the coaxial cable disconnected. Wait 3-5 minutes and reconnect the coaxial cable. Wait for modem to reconnect and then check for IP and service.

@Haziq I sometimes have to unplug several times before it works, but unplugging is a good solution :)

When such thing happens it is usually some cord left disconnected or some key that turned off Wi-fi connectivity. Check all cords and all try manually configuring your router settings.

So I have a little problem with my router.
So a week ago my provider changed my ethernet to gigabit. It was cool, I changed the router to AP300 AC1200 as they recommend. Since I worked from home, I`m an author for dota 2 news, I have to write them every day. And I remember that I have changed some ports on my last router tp-link wr841n, but I can`t change it on the new one, and cause of it, I can`t connect to the site, and can`t work. I watched the guide on youtube, but their advice didn`t help me.

@Bogdanus I suspect this is a ISP (Internet Service Provider)configuration issue so most likely a reboot will not fix it.

You mention a previous router tp-link wr841n does the old one work or is it not compatible with the new connection.

You mention that it is gigabit so does that mean it is a fibre connection?

You also mentioned using different ports?

So not sure what you mean?

Some ISP use vlan taging, I had a similar issue where I had to search the internet for my ISP internet configuration and found they used Vlan.

The wan port is the one you need to make the Internet connection with (also known as eth0).

Hope it helps 

Thomas