If you make a change to something, such as a registration field, a dialog message, or anything that has to do with user viewable output and it does not show up when you test, then you very likely have a cache installed and need to clear the cache.
Before you say, “But I don’t have a cache installed,” make sure that you really know that to be the case. A lot of hosting companies build in their own custom cache plugins and install them as what is known as a “must use” plugin. A must use plugin will be activated on your site, but it does not show up in your plugin panel. Additionally, some hosts apply server side cache applications such as Varnish. So before you say “I don’t have a cache on my site,” make sure you have checked all possibilities of that being the case.
As a general rule, I would recommend that if you are building a new site and are still in the process of making changes (whether to WP-Members or any other part of the site), don’t install/activate any cache applications. If you’re still making changes, running a cache application just makes your development process that much more tedious because you generally will need to clear it to reflect your changes. Wait until your site is built and ready to launch before you install/activate a cache application.