The file strucutre of your project is crutial for this to work. Your SQLDelight files must be in a folder matching the file structure of the java project. Otherwise SQLDelight won't be able to make the generated interfaces accessible in Java.
An examplary file structure would be:
app/src/main/
- java/
- com/example/project/models/
- A.java
...
- sqldelight/
- com/example/project/models/
- A.sq
...