Those quick release adapters are pretty simple (and also simple to disassemble and clean/re-grease). There is only a few things that would preclude their ability to fully seat and allow the detent balls to snap into place: some sort of debris between the end of the steering shaft and the recess in the wheel (which should be obvious), badly damaged sliding splines (again should be obvious), or grit/debris in the release collar of the adaptor (would require disassembly to inspect). Of course the steering wheel needs to be correctly clocked to align the double wide spline on the shaft with the double wide groove in the adaptor, but I'm sure you have sorted.
