Cannot show the breadcrumb

Hi developer,

I am using “Education Hub” theme.
When I try to create the breadcrumb for all pages by inserting the following code in content-page.php, no breadcrumb is shown on any page:
<?php if ( function_exists( ‘menu_breadcrumb’) ) { menu_breadcrumb( ‘main’ ); } ?>
I would like to show the breadcrumb according to the primary menu.
I have ever tried to change from “main” to “primary-menu”, but it does not work.
I would appreciate if you could fix the bug.
Thanks a lot for your help.

Best regards,
Giny