hI , got here a set of 4 eLECTRICAL SOCKETS 40m range silver crest, plugged the first in worked fine, then 4 other ones wont do the learn function, hold learn button, light flashes, I press on remote on A then nothing,I bought it 2 days ago and have already lost the receipt, are they broken or its me who is too stupid to work them out? could it be a bad batch of sockets? thx