Post or site cache still has the old, locked version of the post cached
This is a very common reason which happens due to your host’s server cache, or your site cache. In such a situation, the server or your WP site is showing the stale, locked version of the post to you or to your member. It means that it still did not serve a fresh, unlocked page despite you have logged in.
This can happen if your caching is aggressive, or, you set it to aggressive specifically by turning on one or more option. For example, while using the popular WP Super Cache plugin, if you turn off the option “Don’t cache pages for known users. (Recommended)” in Advanced settings of WP Super Cache, logged in users will be served cached files. Therefore this option should be turned on. So making sure that your caching plugin is not serving cached pages to logged in users is a very good idea.
If you can’t determine any such setting in your caching plugin that may cause this problem, you may contact your web host and ask them whether they have server-wide caching implemented, and whether this caching system serves logged in users stale pages.
Your browser may have cached the page and still showing stale version
Some browsers may show a stale, cached version of a recently visited page if the user returns to the earlier page very soon. You can make sure this is not happening by forcing a fresh reload of the page by using your browser/OS hard refresh feature, like CTRL+F5 which is used for Windows systems.
In rare occasions and for some ISPs, you or your member’s ISP may be utilizing a caching proxy, which may serve cached, stale pages to users for short duration. In such cases the fresh version of the page may be served if you wait a little and refresh the page.