I've been in this situation. Calling customer service, I got the wrong answer because the IP address is not fixed. The customer service suggested that I contact the network service provider to fix the IP address, but I refused. After testing in the dormitory at night, I found the following problems: the office uses dual WAN routers, and once the online banking page is refreshed, the IP address of the external network may change, so the page "Internal system is being upgraded" will always appear every time I pay. Back to the dormitory, I used a single WAN router, and the payment was smooth. A router with dual WAN ports is connected to two external network lines. It is suggested that when using office with dual WAN ports, unplug an external network cable before paying. If you use an internet cafe, it is not recommended to pay. On the one hand, security is not guaranteed, on the other hand, Internet cafes will not let you unplug their external network cables.