I have a problem with menu

Glad to help. May I ask what you are referring to by “main menu”? Is that the WP menu in the Admin Area, or the menu used to switch themes, or some other menu..?

this menu is the main menu of the page. Is only visible on the theme that is set as active in the back room.

When I switch to another theme there is no main menu. it should be because it is set up in the back room.

I’m not sure, but you may not need the Theme Switcha plugin. As stated on the plugin homepage and sticky post in this forum:

What it’s for..

Theme Switcha:

Enables visitors to switch themes via the frontend
Enables developers to build/customize themes privately
Enables you to create links that switch to specific themes
Enables live private previews of any installed theme

What it’s NOT for..

This plugin should not be used together with WordPress features such as Gutenberg Block Editor, Theme Customizer, Widgets, Menus, and other theme-related options. Doing so may result in private changes being made public on the current active theme.

SO if you are trying to, for example, add a menu using a switched theme, it’s not going to work; Theme Switcha only is for modifying theme template files and basic testing, etc.

• This reply was modified 5 years ago by Jeff Starr. Reason: clarity
• This reply was modified 5 years ago by Jeff Starr. Reason: adds infos

I am looking for a plugin that will allow the user to switch between two themes. Your solution could be ok for me.

Yes that is correct, Theme Switcha is great for enabling users to switch themes.