Faild to submit form

Creating Ticktes by Web-form worked well for a while.

Now running in to the error :“Faild to submit form!”

Browser-console output:
Quellübergreifende (Cross-Origin) Anfrage blockiert: Die Gleiche-Quelle-Regel verbietet das Lesen der externen Ressource auf http://yourdomain.de/api/v1/form_submit. (Grund: CORS-Kopfzeile ‘Access-Control-Allow-Origin’ fehlt).

Adding “Access-Control-Allow-Origin” in “/etc/nginx/sites-available/zammad.conf” isnt working either.

Any Idea?

Rebooting the Server a few times does the trick