Error 1: "error: device unauthorized"
• **Cause**: The computer’s RSA security fingerprint has not been authorized on the phone.
• **Fix**: Unlock your phone screen, check the box "Always allow from this computer", and tap "Allow". If the prompt does not appear, go to Developer Options > Revoke USB debugging authorizations, toggle USB debugging OFF and ON, and plug the cable back in.
Error 2: "error: device offline"
• **Cause**: The phone kernel detects the USB connection, but the ADB daemon handshake timed out or was interrupted.
• **Fix**: Run `adb kill-server && adb start-server`. If using a USB cable, try a different USB port directly on your computer motherboard instead of an unpowered hub.
Error 3: "Unable to claim interface" (WebUSB)
• **Cause**: Another background process (such as local desktop `adb.exe`, Android Studio, or another browser tab) is holding exclusive lock on the WinUSB interface.
• **Fix**: Close Android Studio and run `adb kill-server` in your command prompt so the browser can claim the interface cleanly.
Error 4: Phone Only Charges, No USB Recognition
• **Cause**: Cheap charging-only cables lack internal D+ and D- data wires.
• **Fix**: Use a certified USB data cable that supports file transfers.