360 mtu test keeps failing

Using the main computer, open your Internet Explorer and on the Address Bar type http://192.168.1.1

It will prompt your for username and password. By default leave it blank on username and type admin on the password

Under SETUP tab, you can see there MTU, set it to Manual and set the size to 1400 then click on SAVE SETTINGS at the bottom.

Now powercycle your devices. Turn off router first and then modem. Wait for 30sec. Turn on modem first, wait for lights to stop blinking then turn onrouter.

That's it..