the Web MIDI device list is empty or access fails
Nothing useful can be tested until the device or browser path is visible. Start with connection, power, permission and OS recognition before app settings.
Do not jump to the most invasive fix
Do not install unofficial driver packs or firmware from download sites just because the device is missing.
Retest the same condition
The first milestone is simple detection. Only after the device appears should you troubleshoot signal quality or app behavior.
Rule out the simple causes
- 1
Connect and power the controller before opening the MIDI monitor.
- 2
Use a browser that supports Web MIDI and grant MIDI access when prompted.
- 3
Close another app that may have exclusive access to the MIDI port.
Work through the problem in order
- 1
If the controller appears in DeviceOK, the physical USB/MIDI connection and browser-level MIDI path are working.
- 2
If it never appears in multiple supported apps, inspect cable, USB hub/port, controller mode, OS MIDI device recognition, and official drivers where required.
- 3
Do not install third-party driver packages from unofficial download sites.
If the matching DeviceOK test succeeds, prioritize the affected app, browser policy, operating-system setting, or configuration before assuming complete hardware failure.
If the same capability also fails in DeviceOK and another trusted diagnostic path, broaden the investigation to connection, operating-system/device state, official driver or firmware support, and finally hardware.