Hello All, as it is 2020 I am probably a little late on this topic. I Googled "receiver not working" for my son who just bought some technic pieces off Ebay and was having an issue with the IR units. In the results, I came across this thread and signed up for this site. I am new to forums. This may have already been answered, but this is what I found. After opening the receiver, I noticed that they use ribbon cables (the 4 wire flat black cables) and punch down connecters (the silver metal tabs that protrude up through the cables inside (not a great design for something like this). I just used my fingernail and pushed down on the cables on both sides of the connectors and the units started working. Slightly crimping them helps too, but you just have to be careful not to apply too much pressure or risk cutting the wires. Hope this was helpful.
