Detecting voltage at garage door opener control panel wire
Contactless testers are notoriously unreliable.
The best thing to do is to locate the other end of the wire, which should have been connected to your old opener, and check continuity between the BLACK on each end and the WHITE on each end.  There should also be no continuity between the BLACK and the WHITE wires.
These are typically just a simple momentary pushbutton switch that shorts the BLACK and WHITE and that triggers the opener to cycle.
Unlike furnace control wires and doorbell wires, garage door opener controls do not have external power supplies.