Pending payment to Cancelled

Hello!
Please, help me to solve the problem:
using 2checkout plugin for woo commerce each time there is a payment both seller and buyer get the notification of successful purchase from 2chekout and the store, but in the admin area of the plugin, the status of the order is shown from pending payment to canceled without processing or so. Anytime. The 2checkout merchant account is approved, all the necessary settings are followed. Please proceed