You have enabled "Allow Effort Task Creation" to projects and custom investments. It is working for projects created without selecting a Project template however, it is not working with a project template.
Release : All supported releases
Component : CA PPM PROJECT MANAGEMENT
This can happen when the Project template was created before "Allow Effort Task Creation" was checked and therefore did not contain effort task.
To overcome this, current templates will need to be modified.
Then it will work without having to recreate the template. The benefit of the effort task is that all staff that is assigned to the project are automatically assigned to the effort task, which is not for any other types of tasks that do not have an ID ~rmw.