User with status ‘unsubscribed’ tries to subscribe via the regular form

If someone who has been a subscriber already, then unsubscribes and afterwards tries to subscribe again via the regular subscription form and using the same email address as before, there is an error message saying the subscription failed.

In the plugin settings, I allowed repeated subscriptions (sorry, I have German language files active here, so I do not know the exact wording). I would have thought that this would handle the problem, but it doesn’t. Is there any other chance to change the plugin behavior?