When developing a Flask machine learning application, particularly one that predicts the cost of electric vehicles, problems such as TemplateNotFound can abruptly stop development. These issues frequently have to do with missing or incorrectly set HTML files, including index.html, which are essential to the operation of the application. Verifying directory paths and file names is crucial because Flask depends on particular folder structures for templates. Using commands like os.path.exists and implementing strong error handling will help you identify and fix these problems efficiently so you can resume working on the project.