Run the check
On a page with room to scroll, move the wheel slowly in one physical direction and record both page movement and the scroll test's event direction.
Locate the current scrolling-direction control in Windows Mouse settings or macOS Mouse settings; use the official screenshot for your system, and change only that control.
Repeat the same wheel motion on the same page and in the scroll test; if only one app differs, check its own scrolling preference.
Official reference: Microsoft scrolling-direction setting
Official reference: Apple Mouse settings and Natural scrolling
Read the result
A persistent reversal across apps that follows one direction setting differs from isolated wrong-direction events during otherwise normal scrolling.
Limits and next step
Wheel delta signs are browser-observed and may be transformed by the operating system or driver; this page cannot change those settings.
Repeat the check after changing one setting or connection. Keep a record of what changed before deciding whether the device needs service.