Hi Yinxiao,
Sorry to hear this is still not working for you. Maybe you can have a look at the example fpm application /BOFU/DEMO_SALES_ORDER in package /BOFU/DEMO.
Have a look at the FPM_EDIT_MODE of your application configuration: the default option 'not supported' should do the trick. This way the application should start in read only mode, and after clicking the global FPM_EDIT button the fields should become editable. (if the checkbox 'read only mode' of your list UIBB is deactivated).
You can also opt to open your application in edit mode, see FPM BOPF form UIBB fields disabled
and ** TEAM FPM ** - Display/ Edit Mode in the FPM OVP Floorplan
Hope this solves the issue.
Kind regards,
Bjorn