Error sending data into Marketing Hub

Error sending data into Marketing Hub

I created a flow that sends data into Zoho Marketing Hub. During test, the flow works fine. But during live execution, the flow fails. The error message is: Zoho MarketingHub says "Fehler beim Abonnement. Bitte warten Sie etwas ab, versuchen Sie es dann noch einmal." (Error with your subscription. Please wait a moment and try again).
Any ideas? Thanks