It might be a little 'off' and perhaps too far away? - Black-bit in-line with magnet, and perhaps a little less gap?
We any also be a a point where you need a local, tame DCC user?? - I fear a CV will need changing.. Just need to find the 'damn-paperwork'..
T'would appear to be CV 64, but the paperwork, so far, is less than helpful..
Adjusted the sensor to the point of a minuscule separation between it and the magnet. Still no luck.