Controller Not Detected
If the gamepad tester support status says no controller is detected, connect by USB or Bluetooth, focus the page, and press any controller button. Many browsers do not expose a gamepad until a user action occurs. If nothing changes, reload the page after the controller is already connected and try a different button. This controller test troubleshooting step solves many first-run detection reports.
For USB, test another cable and port. Charge-only cables are a common reason a controller test never sees hardware. For Bluetooth, remove old pairings, pair again through the operating system, and confirm that another application is not capturing the controller exclusively. Controller diagnostics are only possible after the operating system exposes the device to the browser.
Try a current desktop browser before assuming hardware failure. Mobile browser support is inconsistent, and some embedded browser views block the Gamepad API. If one browser detects the controller and another does not, the support path is browser compatibility rather than repair. Keep the gamepad tester support page open while comparing so each controller diagnostics support step is repeatable.