No power to trailer brakes, 2007 Sequoia

Gents,

I have a new-to-me '07 Sequoia with the factory tow package. It appears no trailer brake had ever been installed. The plug still had a female dead plug attached, was wrapped up in electrical tape, and buried deep in the bowels of the wiring mess behind the kick panel. It took me quite a while to find.

All the lights work on my Curt 7-pin trailer tester, except the brakes (BK). With the REDARC Tow Pro Elite brake controller installed, the tester shows a constant very faint glow at the BK test light, even without the engine running. Without the controller hooked up, that light is completely out, with or without the engine running. That light does not come on when the brakes are applied, with or without the controller installed.

I've cleaned the 7-pin connector, as many of the grounds as I can find, checked fuses, which were all good, but I replaced them anyway. No change.

Any ideas would be greatly appreciated.