Springboot Form failure: The context path is either empty or not defined

Hello,

i have a problem. I want to download a file, so that it can be filled by a user. Therefor I create a simple html file. I’m using Springboot and Java and followed all steps of configuration for embedded forms. But I get still this notice: Form failure: The context path is either empty or not defined.
Can someone help me?

Could you post your project directory structure and your modeler configuration for formKey?