Redmine

Hi all
I'm new here, but have already found this question in Redmine's Forum via Google... but no answer that helps me...
My Redmine is running so far, but when I try to create a ticket, I get the answer in the subject above. And when I try to create a tracker, I get the answer 'Default status' must be filled in. In the Default State drop down I see a check mark, but I can't save the selected state. Somehow I am going in a circle.
I have activated Redmine version 3.3.10.stable on a Synology Nas as a docker.
Can anyone tell me what I need to do to create a ticket?
Thanks a lot!

Translated with www.DeepL.com/Translator >> my native language is Germam so DeepL helped me to translate ;-)