Fields added in WordPress Pages do not appear on the Live site or Preview Changes

If you have a caching plugin active in WordPress, you may need to clear the cache from the Dashboard then refresh the frontend page in your browser. Most caching plugins I've seen add a link for clearing the cache to the bar at the top of the page when you're viewing the Dashboard.

Thanks Terry
i installed WP Super Cache and clear Cache Contents but nothing happens

Perhaps you could open your browser's dev tools and check the console for any javascript errors appearing on the Edit Page?

I'd take Terry's suggestion one step further.

1) Clear your cache.

2) Disable your WordPress caching plugin during development.

3) Disable your PHP Opcache caching during development (far more maddening than WordPress caching problems).

4) Enable WP_DEBUG in your wp-config.php file + check your debug file first, whenever you hit a problem.

For the problem you describe, I'd camp on the debug.log file (as in tail -f debug.log) + then test every step of your process, like watching what emits in your debug file when you hit save or publish.

If you can't camp on your debug file (no ssh access), then you have two other options.

1) Do one operation + download your debug file via SFTP + review changes.

2) Mount your WordPress DocumentRoot (install directory) onto your local machine (use curlftpfs) so you can camp on your remote log from your local machine.

Sounds like possibly a database error being thrown, which isn't reported correctly.

Ah... Also be sure you're running latest WordPress, which today is 4.9.8 so you have all recent bug fixes installed.

Thanks all
@David Favor
after enable debugging mode i got this error
Warning: count(): Parameter must be an array or an object that implements Countable in /home/j6tiri37j06d/public_html/mydomain.com/wp-includes/post-template.php on line 284

and this

Warning: Declaration of Nav_Walker_Nav_Menu::start_el(&$output, $item, $depth, $args) should be compatible with Walker_Nav_Menu::start_el(&$output, $item, $depth = 0, $args = Array, $id = 0) in /home/j6tiri37j06d/public_html/mydomain.com/wp-content/themes/mydomain/functions.php on line 514