Failing with integration of Kostal Solar Inverter

I try to integrate my Kostal Inverter via the Integration tool in HA. Found the “Kostal Plenticore Solar Inverter”.
But if I try to make a connection with the correct host-adress and the correct password HA says:
Verbindung fehlgeschlagen
I have copied the host-adress from the browser…

I must say, this is my first day with HA