What you want to ask is the reason why you can't display the second menu if you click the first menu according to the frame? The reasons are as follows:

1. Wrong frame setting: Check whether the frame setting is correct, and the display mode of the secondary menu is not configured correctly, which will lead to the failure to display the secondary menu

2. Compatibility problems: different browsers have different support and analysis for the frame, which leads to the failure to display the secondary menu in some browsers.