It might be not your case but if behind the scene permalink settings have been switched from default one, then the request:
?category_name=slug1+slug2
is rewritten to
/category/slug1/ or /category/slug2/
so only the posts from one category are shown.
Related Posts:
- is_category() in pre_get_posts strange error
- Rearranging posts based on categories
- Custom Query to search through categories
- How to query all posts of a specific category, and any other category combination
- is_category in pre_get_posts results in php notices
- Query the Loop without breaking it
- How to Check if a Child Category is Being Queried
- How Do I Merge Categories With phpMyAdmin
- Category archive page – loop through posts of certain tag (with pagination) – pre_get_posts
- If newest post of category is newest post in general, skip first post of category
- Disallow categories from this MySQL query
- Include posts from feature category in pre_get_posts
- How to display posts under a specific subcategory of a given category
- get_the_category and echo out link to child-most/deepest category
- query in category.php repeats itself
- Display posts separated by Category in Author’s page
- Category param redirect to post type archive
- How to get related tags based on a category?
- Show popular post by category code
- How to get latest posts from each category in regular order
- category pagination got broken suddenly
- How to query categories with Advanced Custom Fields?
- Where and when does WordPress invoke routes
- And/Or Category Query
- Exclude category from query
- Overriding default calendar to show posts from a category
- function query_posts disabling current_page_menu class
- How Do I Delete WordPress Posts Older Than 400 Days, From A WordPress Category
- Using in ‘category_name’ in ‘$query->set();’?
- custom query for both category and pages using global $wpdb;
- Get categories of queried posts
- Query from multiple category (and)
- How to display posts from specific category using get_option function?
- SQL query to get posts from multiple categories but not in a category
- Conditional category query breaking?
- How to filter post from categories only if the posts appears in one of them, not the other?
- Category name for all posts getting assigned to a single random post
- Show Posts via cat+cat in URL that are in both Categories doesn’t work
- List of post categories only associated to another custom taxonomy
- how tho change number of posts in loop from specific categories
- Get category from slug list
- Issue with WordPress category search
- Querying posts from two different categories while looping inside another loop
- how to get postmeta info based on multiple categories?
- Too many categories drastically slow down my website
- How to get posts from many categories using WP_Query
- Is it possible to query the result of a query?
- Match two taxonomies to display a specific content
- Category slug in in loop always the same?
- display certain category on custom template page
- Detecting top parent category fails on home page
- How to use Greek characters/letters in a query?
- Displaying posts by year
- wordpress category.php query for featured news item, broken pagination and repeating posts
- How to show posts of a specific category
- How to get parent and child sub category (Taxonomy) order to display
- How to query by subcategory and, if there are fewer than 10 posts in that subcategory, fill out with posts from parent category
- How to make query loop block dynamic
- How to create an automatic MultiColoumn MegaMenu with Categories WordPress
- Is There a Difference Between Taxonomies and Categories?
- List all subcategories from category
- How To Find Out WordPress Category Table in MYSQL?
- Add custom field to Category
- Get Category ID inside Category template
- Only one category per post
- WordPress Multisite – global categories
- Get the children of the parent category
- Get posts from sites in Multisite?
- WP REST API: filter by category 1 AND category 2
- How To Get Parent Category Slug of Current Post
- Display All Products by Category with WooCommerce
- What is the difference between a “tag” and a “category”?
- Is there an easy way to make a meta box have the tabs like the Categories meta box has?
- How to check if I’m on the last page of posts?
- Display posts from the same category using next/previous post link
- How would I get a taxonomy/category list inside a Gutenberg block?
- Can I set a default featured image for a category?
- Check if a post is in any child category of a parent category
- How to export and import taxonomies (category, tag and/or custom taxonomy) and their terms
- Force category choice before creating new post?
- Gutenberg editor add a custom category as wrapper for custom blocks
- WooCommerce: List All Categories
- How to get category and archive title?
- Get category ID from category slug (not working)
- How do I remove “Uncategorized” from posts with more than 1 category?
- Get rid of WordPress category, tag and author archives?
- Individual rss feed entry length for categories?
- How can I create a category landing page followed by pages of posts?
- Remove parent category from permalink? Basically only have the child category?
- Custom permalink structure leads to be 404 on pagination
- Retrieve Product category ‘NAME’ by product category ID – WooCommerce?
- Posts URL structure like site.com/category/the-post-title
- Can’t custom taxonomies have same terms (slugs) as categories?
- How to get permalinks with category base working with sub-categories
- How to remove the term “category” from category pagination?
- Using wp_category_checklist in a widget
- WP 3.9 TinyMCE no longer loads on category description editor
- On the category page, get the category object
- Get only the top level categories using get_categories() without foreach loop
- Get all categories and posts in those categories