network problems. Yunzhong Gourmet APP is a widely used online ordering software, which helps users to place orders quickly and buy all kinds of delicious food with confidence. The reason why you can't log in to the app is because of network problems. See if WiFi is connected or the traffic is turned on. APP is the abbreviation of Application, which means "application program". Simply put, it is mobile phone software, which mainly refers to the software installed on smart phones.