When I paired the second extender to the network it worked fine at first, however after about 5 minutes I noticed there was a conflict, where one of the two extenders would loose connectivity to the net. I noticed that whichever Extender had lost connectivity would have a Class B I.P. address, for some reason, even though each were configured "out of the box" with Class C addresses. Obviously I thought that there may be an I.P. address conflict at first, that both extenders attempting to use the one subnet mask might be at fault, and so I tried to set each power line extender to separate sub-net masks.
I kept the original extender on 192.168.1.X : 255.255.255.0
I set the new extender to 192.168.10.X : 255.255.255.0
Unfortunately when I change the I.P. address and Subnet mask settings through the bundled TP-Link utility, it doesn't seem to save the changes, and even on reboot the extender that has lost connectivity will not have regained it and will still have a Class B address of 169.254.X.X.
I've a fair bit of experience mucking about with routers etc., but these particular TP-Link extenders are new to me, and help identifying the problem would be really appreciated.
I would use an address on the same network, you have them on two distinct subnets with 1.x and 10.x so they will not communicate. They should be on the same network as the router and their addresses are static so make sure that the router DHCP cannot assign those addresses.