LIGOCAM shows H1:PEM-EX_MAG_VEA_FLLOR_X/Y/Z_DQ as disconnected. I confirmed that (i) the magnetometer was still in place (ii) the power supply was on and (iii) the magnetometer box was running. I couldn't follow the triaxial signal cables from the box to the PEM racks - the cables are bound up with a whole bundle under the beamtube near the BRS. I still don't know why they're marked as failing.
I took a look at the ASD of EX Floor magnetometer and compared it to a couple magnetometers that are marked as working. The ASD does look flatter and lower magnitude than working magnetometers.
An easy way I used to check magnetometers was to wave a fridge magnet near the magnetometer while monitoring the current power spectrum on a laptop.