What's the hardware and firmware version of your router? Some routers cannot set up parental control to block all internet, have to enter the web site address, otherwise none of the children...

What if you disable IGMP snooping? If no luck, contact support@tp-link.com

If smart connect is turned on, changing channel does not matter. Could you turn off smart connect to see what happen? Does this happen on your computers? Make sure you have installed the latest...

It's 128 AES, cannot be changed.

Is the wifi led always lit up? I guess the router has two wifis, 2.4G and 5G, both have the same issue? Do you install the latest firmware version?

Sometimes the online checker may not be correct. You can do a telnet test on your computer. And you can also set a DMZ host for the gaming console.