No message shown after subscription

On this page https://www.sibyllalustenberger.com/ the subscription form in the footer is not working properly. There are no messages shown when subscribing. The page is just jumping to the top with the link https://www.sibyllalustenberger.com/#wysija
Confirmation Emails are sent.

I read somewhere that this might be a JavaScript error, so I deactivated all plugins. No change.

Then I loaded the Plugin JQuery updater to update to jquery V2.2 instead of the wordpress bundled 1.12. With that the messages are shown at the subscription form in the right way. But unfortunately this breaks the Theme, so I go back to JQuery 1.12.

Have you got any idea how to get this working?

Thanks a lot
Jürgen

https://www.ads-software.com/plugins/wysija-newsletters/