Some of my EPOC+ sensors remain BLACK. What should I do?

Make absolutely sure the sensor consists of a body, felt pad and gold plate, correctly assembled and identical in appearance to all the others. Also, make sure it seats properly in the socket, with a definite click. It should not rotate freely; it should be latched in place. Inspect the socket closely to make sure it appears properly assembled – you should see the 3 metal contact springs directly by pressing against the inside of the housing, there should be no apparent gaps in the sides of the socket (they are clipped together, very rarely the clip is not assembled properly and just needs to be squeezed together). Compare it with all the other sockets.

Electrical bench test

Thoroughly soak each sensor, then turn on the headset and get a connection.
Grasp one reference sensor with one hand and the other reference sensor with the other hand. Pressing your thumb against the sensors should work well.

Now, touch one or more of the other sensors. Each one should lighten up a second or two after you touch it. This requires a little dexterity, but it’s not too difficult. Next, touch the suspect sensor. If it does not lighten up, and the same sensor location does not lighten up even if you swap in other sensors known to be working, please contact support. There may be a broken internal wire. If you ever see that sensor lights up even to red, the wiring is perfect and there is some other issue.