powerline device will be affacted by the electric power environmental, you can check whether there are any high-power electrical appliance running at night, and try to move the device away from them....

You can try to enable the remote control function on the V1, look at this manual https://www.tp-link.com/en/faq-2322.html, it will allow you control the plug in any networks.

If your firmware version is the EU version you can try to upgrade to the latest firmware 160708. https://www.tp-link.com/en/download/Archer-C3150_V1.html#Firmware

I couldn't go to some websites before, I then change the DNS to 8.8.8.8 and 8.8.4.4, turn off the parental control settings fix the issue. You can try that..

I changed that port number once, you can check the menu under Advanced-system tools-administration

I got this from TP-Link long time ago: we have already considered the security issue, and have already blocked the related SSH tunnels and commands, which makes this SSH available only to the Tether...