You can put the 2nd TP link in the same house, and test the internet speed. Have tested the speed with a cable connection or wireless connection?

Put the two powerline adapters close to each other. And press the pair button of one of the adapters, and hold on it for 3-8 seconds and release it. Go to the second, do the same thing: press and...

have you tried unplug and plug back the 3G modem? Maybe you can contact the tp-link support for some help.

If your link the computer to the router with a hard wire, is there the same problem

you can contact the tp-link or ZTE to see if there is a sniffer to make a binfile.

I not quite familiar with Linux. But you can connect the range extender to the computer with a cable, and set a static IP like 192.168.1.10 ans subnet mask 255.255.255.0 on the LAN connection on your...