First and foremost, save the post/page you're working on and then clear your browser's cache & cookies. Then re-login to the WordPress site, open your post/page, and try publishing it again.
Typically, people encounter this issue for one of three reasons:
- A caching mechanism, such as WordPress Cache or SuperCache, is serving up the older version of the page you're trying to update, or...
- WordPress has been set up to require someone with higher-up account privilege to approve pages/posts before they will appear on the site, or...
- Your account privilege simply isn't set high enough to allow for publishing.
In such cases, whoever installed/setup WordPress for you would need purge/clear the WordPress Cache or SuperCache, and/or check that your account has enough privilege to publish posts/pages, especially without need for approval from another user.
Otherwise, if you've been able to publish before without issue, or if you know your account has 'Administrator' or 'Editors' privileges, there may be a more technical error that the site's webmaster/administrator will need to personally attend to.
In any case, if you don't have access to clear the WordPress Cache/SuperCache, and saving your post/page and then clearing your browser's cache/cookies doesn't work, this likely isn't a problem you'll be able to solve on your own. :-(
Reply back and let us know if we can help further - Best of luck!