There is no solenoid in this actuator. It employs solid state circuitry.
When power is applied to the device, battery voltage at the brown, pin D, and ground to the black, pin C, the device takes pin A, the control wire, "high" to battery voltage or thereabouts.
When this "high" is taken "low" by grounding, then the device activates its' motor and drives the plunger out.
One thing that can be done to verify the backprobing is to NOT ground your test lead at first, but instead check for voltage there.
When power is applied to the device, battery voltage at the brown, pin D, and ground to the black, pin C, the device takes pin A, the control wire, "high" to battery voltage or thereabouts.
When this "high" is taken "low" by grounding, then the device activates its' motor and drives the plunger out.
One thing that can be done to verify the backprobing is to NOT ground your test lead at first, but instead check for voltage there.