I had no trouble installing 2 patio motion detector lamps 30 yrs ago. When one (Lamp A) failed 2 yrs ago, I replaced it with a similar one, and all worked well. The older second one (Lamp B) finally failed recently. However, despite trying 3 different motion detector lamps, I have been unable to get this second one (Lamp B) to work as its predecesor. When I measure the voltage at Lamp B, I get 120v. Yet, when I install the new second lamp, it does not come on. All the 3 lamps I'd tried as replacements work when I tested them in the garage on another circuit, so I suspect that the replacement lamp (Lamp A) I'd installed 2 yrs ago must somehow be interfering with the installation of the new second lamp (Lamp B). Any suggestions to a DIY who'd taken 8th grade electric shop only? ;-)

A lot of 2 light issues occur when they are paired. The last one I installed, 1 week ago, $19@HD, had 3 different schematics and different wiring layouts. Some use the red wire, some don't. Re-read the instructions to see if you have it set up as a master/slave or stand alone.