What happens is probably related to the theme. The user goes through the login process of entering the username and password and this action appears to succeed. However, instead of the site presenting them with the usual content relevant to a logged in user, they are presented with pages that appear to be for guests – including every page having the ‘login’ button displayed. Other plugins respond in the same way, for example, one that shows forums with unread posts that assumes it is serving a guest and behaves accordingly.
I did not try to actually post anything as a logged in user – I needed to fix my site so just disabled the plugin so I’m unsure whether the problem was functional (which I suspect) or aesthetic (theme related) but in any event it was a problem.
I hope you can find out what the issue was because the idea of the plugin is great and very useful! I write code myself as a hobby so if I can be of any further help please ask. Obviously if nobody else has an issue then it’s something I’m doing wrong!