Approach to clearing old codes: Long press the two ( Lock & Unlock ) buttons to clear old codes(The LED indicator will flash once, which is the sign of cleared state).
Approach to duplicating: Place them side by side(as close as possible), then press both one key of your old remote and the to-be-matched key on this remote simultaneously. The LED indicator will flash once. Learning process done. Other keys accordingly.
Approach to recovering: Press the Start and Mute buttons for about 2 seconds till the light is on and flicker. (Or you can delete the codes and repeat the learning process.