Solution:
The answers on the Internet have been verified by me to be unreliable. In the future, everyone will know that the solution for Flexigrid not displaying data under IE is: specify the Ajax request method as Get method
In addition, it’s not that flexigrid cannot use the “post” method to send data, but the “post” method must have data for post under IE. For example, you can use the post method when paginating, but you don’t have any data. If you want to send, you must use the "get" method. Other browsers may not have strict requirements for this, but IE has stricter requirements: