2008 Ford Ranger ABS issue?

2008 Ford Ranger with an ABS problem. ABS activates constantly under 25 mph. But once I hit 25 MPH the light comes on and the brakes work great at all speeds until the truck is shut off, then the problem restarts.

I have installed new pads and rotors, making sure the ABS ring is on each rotor, and identical to the worn out parts I replaced. I replaced one front ABS sensor due to damage, the other front sensor tests good. Rear sensor was pulled and cleaned, not sure how to test. Had shop diagnose the light, but the test came back "ABS system unresponsive".

Any help is greatly appreciated.

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