It is a general question please check following steps and provide detail log if needed:
Check your input data: Ensure that the input data you're providing for model training is in the correct format and adheres to the requirements specified by the Form Recognizer service. For example, check if the file is in a supported format (such as PDF or image files), and the file size is within the allowed limits.
Verify your API endpoint and authentication: Double-check the API endpoint and the authentication credentials you're using to access the Form Recognizer service. Make sure the endpoint is correct and the authentication token is valid.
Review your code or SDK version: If you're using a software development kit (SDK) or a custom implementation to interact with the Form Recognizer service, ensure that you're using the latest version and that your code aligns with the documentation provided by the SDK or the Form Recognizer service.