Check the (I think it is Yellow) wire from the switch to the dimmer switch.
With the HL sw in the 'on' position---you should have 12vdc to the center wire on the floor dimmer.
If not---perhaps that wire pulled loose from the HL switch connector.
not all that uncommon.
If it has pulled from the connector----try to completely remove it (noting the position and orientation in the connector) and bend the tiny tab on the back of the terminal out a little bit. This is the locking tab, and should lock the terminal in place if the connector is not damaged.
If you have voltage at the dimmer switch, but no voltage on either of the outboard terminals----dimmer is bad.
Be a good idea to replace it anyway-----I had one of these monsters start a fire on my floorboards as I was clipping across Calif Hiway 58 @ 75mph, on a very dark night (2am).
Instant lights out!!!!-----FIRE
75mph in the dark----with a fire on the floor------NOT FUNNY