Exceprt not displaying

According to your question:

What is the main reason of loop?

the clearest answer comes from official documentation:

The Loop is PHP code used by WordPress to display posts. Using The
Loop, WordPress processes each post to be displayed on the current
page, and formats it according to how it matches specified criteria
within The Loop tags. Any HTML or PHP code in the Loop will be
processed on each post.

When WordPress documentation says “This tag must be within The Loop”,
such as for specific Template Tag or plugins, the tag will be repeated
for each post.

It’s correct put within the loop the_excerpt() template tag.

For example a loop code it might looks like:

<?php if( have_posts() ) : while( have_posts() ) : the_post(); ?>
  <p><?php the_excerpt(); ?></p>
<?php endwhile; else: ?>
  <p>No posts were found</p>
<?php endif; ?>

To help you with your issue, it could be a good idea posting the whole code

Related Posts:

  1. Jquery Slider for profile template
  2. Get excerpt using get_the_excerpt outside a loop
  3. Should I use loop in the single.php file?
  4. wp_list_categories: get latest featured_image of category
  5. WordPress Alphabetical Glossary close div in loop
  6. get_the_foo() in the loop – does it perform another query?
  7. Exclude filter on front page
  8. category__not_in — anyway to use category name instead of id?
  9. Filtering posts by multiple taxonomies
  10. Check if date of post is yesterday
  11. Exclude first 2 posts with meta_key from loop
  12. Fix inefficient loop breaks post.php on form submit
  13. Make a custom loop inside single.php with pagination
  14. Why do I get `Call to a member function have_posts() on a non-object `? [closed]
  15. Help with Changing loop.php?
  16. the_content() seems to block my ACF-code
  17. Pulling current post/page data into header.php
  18. Loop and Page template : my WP_query don’t take args
  19. How to split a loop into two columns
  20. Category Ajax call
  21. Change front-page layout after x amount of posts ( while in the same loop)
  22. Transient loop issue
  23. popular post weekly and monthly
  24. How can i use the same template file with a widget and category loop?
  25. WordPress Loop inside Loop?
  26. Get single post from tags array
  27. Apply an Incremental Counter in an Array Function
  28. Get all posts including sticky ones with get_posts(),setup_postdata(), and foreach loop?
  29. angularjs not displaying all posts
  30. Latest Post Styled Different Than other Posts
  31. ACF custom field in [closed]
  32. Split wordpress loop to multiple layouts
  33. Woocommerce: How to display product price [closed]
  34. Update status of all posts in a category
  35. is_active-sidebar loop
  36. Unable to change the “Read more” text inside the_excerpt
  37. Conditional: IF current user has NOT commented on current post (not including post author)
  38. Can I add generic numbering HTML classes to items as a loop runs?
  39. Add “showing posts x to x of y” in custom post type paginated loop
  40. Change post order by meta key, per post basis
  41. Custom Post Type on Homepage – Studiopress Genesis Framework
  42. New loop vs widget
  43. Display a single category in blog section
  44. Query Nopaging action not having effect
  45. Yoast taking over my WordPress title tag [closed]
  46. Pagination broken after using 2 loops to show content
  47. Getting page slug
  48. How to get pagination to work with 2 wordpress loops
  49. How do i find and restore a sidebar that i accidentally deleted? [closed]
  50. Exclude page from loop results
  51. How is WordPress changing the content markup?
  52. Inserting CPT and static content at every X post, is this possible?
  53. loop through posts and display inserted media and post title as a link
  54. using update_user_meta to rank users
  55. Can’t grab author info outside of the loop
  56. Custom Blog Loop on Home Page
  57. Where to add offset?
  58. How to synchronize The Loop with the max post per page?
  59. How to add a byline to all the pages?
  60. How do i create a list-posts-page?
  61. Exclude posts based on an array
  62. Displaying member join date on page
  63. Ascending order has strange effects on wordpress loop
  64. List ALL posts by author on author archive
  65. get post images to link to external sources
  66. Using is_page_template inside loop
  67. How to show the last article in a different way in my blog?
  68. Can’t limit posts_per_page in loop
  69. Slug is changing when I use WP_Query in a metabox of a post
  70. How to fix pagination for custom loops?
  71. Check to see if a field is within an array in twig
  72. Custom loop not working in singular.php, working in other pages
  73. Loop Posts Outside of WordPress Installation
  74. Strange problem with wp_get_attachment_image_src database (db) query count
  75. How to include posts from one category, into a separate category of posts?
  76. how do i make this loop work
  77. Archive sorted by month – separate
  78. Making a specific page wordpress compatable that is not index
  79. Humanmade | Custom meta box class: How to display a repeatable meta box group?
  80. Can’t print out returned value
  81. change the_content images for different sizes (Desktop, tablet, mobile)?
  82. Get query result before posts are displayed?
  83. WordPress Group By Problem
  84. display only parent replies count in index.php
  85. Home page loop with pagination problem
  86. WooCommerce custom loop pagination on front page
  87. Eliminate duplicates in a foreach loop [closed]
  88. Tag custom loop show posts
  89. While loop inside another while loop
  90. Problem with ms-thumb-frame-selected class in Master Slider
  91. I want the first post on my home page to be lengthier than the rest (example included)
  92. Loop with Custom Post Type Taxonomies and Interstitial Code
  93. Question about custom plugin
  94. loop mix my child-category and parent-category
  95. Fix html inside a for loop [closed]
  96. How can you make it so the comment box shows on some pages or posts but not all?
  97. Insert multiple custom components after x-number of posts
  98. wp_mail sending only once inside foreach loop
  99. How to use orderby on meta_value when using Pods custom database table storage
  100. How to set and retrieve cookies while in the loop