| Problem | Likely Cause | Solution | |---------|--------------|----------| | “Device not recognized” | Missing or corrupted drivers | Reinstall drivers manually from the Drivers folder. Disable driver signature enforcement. | | “Verification failed at address 0x0000” | Poor connection or power issues | Check wiring, reduce programming speed (in Settings > Timing), and ensure target device is powered externally (not just from programmer). | | “Timeout error on USB bulk transfer” | USB selective suspend | Disable USB selective suspend in Power Options > Change plan settings > Change advanced power settings > USB settings. | | “Cannot open COM port” | Port conflict or permission | Close any serial monitor (Arduino IDE, PuTTY). Run Willar as Administrator. Change COM port number in Device Manager (right-click COM port > Properties > Port Settings > Advanced > COM Port Number). |