Newsletter plugin doesn't work anymore as it should be

Hello,

Since I’ve updated the theme, my newsletter plugin doesn’t work anymore like it should be. I’m working with the Wysija plugin. When someone subscribes, unsubscribes or want to change their settings, the loginpage appears and not the message that should be appear, like “you are successfully unsubribed” or “you are successfully subscribed” or the page where they can change their settings … What can I do to fix this problem?

Thanks a lot!