Wifi smart socket s26

I was not using my socket for a long time. And now I need it but i can turn it on and off from the butten but I cant get in to pairing mode. How can I reset the socket seittings

Please refer to the following manual for pairing:
说明书 Sonoff S26 200x90mm 105g铜板 四色印刷 手风琴4折 V1.3