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Please give us a description of what happened

I noticed this issue with a multisite but this should affects any site which uses a permalink structure with a custom front like /blog/posts/%postname%/.

In my case the $blog_prefix was set to blog/ which means any access to /blog/posts/<category-name>/ lead to a 404 page.

Related code:

Note that the /blog prefix is no longer required as of https://core.trac.wordpress.org/changeset/34749.

To Reproduce

Step-by-step reproduction instructions

1. Create a multisite which is not a subdomain install
2. Use /blog/posts/%postname%/ as the permalink structure for the main site
3. Create a post with a category
4. Try to access the category archive

Expected results

1. /blog/posts/<category-name>/ returns the category archive

Actual results

1. /blog/posts/<category-name>/ returns a 404 page

Screenshots, screen recording, code snippet

If possible, please provide a screenshot, a screen recording or a code snippet which demonstrates the bug.

Technical info

• If relevant, which editor is affected (or editors):

• Block Editor
• Gutenberg Editor
• Elementor Editor
• Classic Editor
• Other:

• Which browser is affected (or browsers):

• Chrome
• Firefox
• Safari
• Other:

Used versions

• Device you are using:
• Operating system:
• PHP version:
• WordPress version:
• WordPress Theme:
• Yoast SEO version:
• Gutenberg plugin version:
• Elementor plugin version:
• Classic Editor plugin version:
• Relevant plugins in case of a bug: