I have successfully binded one of my 3 existing TL-MR100. None of the others will bind. And if I try to bind, using the TP-Link ID menu, it says " Unable to connect  to TP-Link Cloud". I have checked with the diagnostics and it tells me that everything is OK.

There is a difference in hardware and software versions:

working -

FW 1.2 HW V.2

Not working - 

-FW 1.3 HW v.3

-One more, but do not know the FW or HW version (not accessible from home).

-One MR400 FW 1.3 HW v.4.3

I find it hard to think that the oldest FW and HW version on the router has the feature and not the new ones, but maybe it is so? Anyone got a TL-MR100 with newer that FW 1.2 HW V.2 got it to bind?