[wp-trac] [WordPress Trac] #51904: Critical Issue: Appearance > Menus Editor does not work in subsites

[WordPress Trac]

#51904: Critical Issue: Appearance > Menus Editor  does not work in subsites
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 Reporter:  javad2000                            |      Owner:  (none)
     Type:  defect (bug)                         |     Status:  assigned
 Priority:  normal                               |  Milestone:  Awaiting
                                                 |  Review
Component:  General                              |    Version:
 Severity:  normal                               |   Keywords:
  Focuses:  multisite, performance, coding-      |
  standards                                      |
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 Hello
 I recently moved from WP single to WP-MU for the first time, but a very
 frustrating bug prevents me from using WP-MU.
 I have a main site (mysite.com) and a few subsites (mysite.com/site1 ,
 mysite.com/site2)
 On the main site, when I go to Appearance > Menus, the menu editor
 dashboard works OK, I have no problem with it. For example, there are a
 few headings (pages, posts, categories, custom links, etc). I can click on
 each heading in order to expand/collapse the sub-items in order to see a
 list of posts, categories, etc. I can easily add posts, custom links,
 pages or categories to the menu.
 On the subsite, when I go to Appearance, Menus, the same headings are
 available (Pages, Posts, Categories, Custom Links, etc.). The first
 heading (pages) is expanded, so I can see a list of pages, and I can add
 pages to my menu. However, other headings (custom links, posts,
 categories, etc.) are collapsed, and cannot be  expanded. I cannot add any
 custom link, post, category, etc. to my menu. The subsites are useless
 without menus. I cannot launch my website without menus.
 I deactivated all plugins, but no luck.
 I use the latest version of WordPress (5.5.3) with the default theme
 (Twentytwenty).
 I installed a new and fresh version of Wordpress multisite  with a new
 fresh subsite, but the problem still exists (the menu editor works on the
 main site, but not on the subsite). That's why I believe there is surely
 something wrong with the core.
 I tested the problem on several PCs with different OS and different
 browsers (Chrome, Firefox, IE), but the problem exists on all browsers,
 all PCs, all OS's.
 Since I am blind and I use a screen reader, I firstly thought there was
 something wrong with the accessibility of the page, so I opened a support
 topic in Accessibility Forums:
 https://wordpress.org/support/topic/appearance-menus-accessibility-
 problems-for-blind-users-with-screen-reader/

 Nobody replied the post. Later on however, I asked a sighted person to
 click on the menu, and found out, the problem had nothing to do with my
 screen reader. Even sighted people cannot use the menu editor. I tried to
 open a similar topic in "Fixing Wordpress" forums, but, the moderator
 closed the topic for being repeated.
 The problem still exists and I cannot launch my website. Please try to
 reproduce this bug and give your feedback here. Is it a bug or something
 wrong with my server?

 Thank you

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Ticket URL: <https://core.trac.wordpress.org/ticket/51904>
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