The error message "Value cannot be null. Parameter name: url" typically indicates that a URL or file path is missing or invalid in the Atmel Studio project. After upgrading to Windows 10, it is possible that some settings or dependencies have been altered, causing this issue. To resolve it, you can try checking and correcting the project settings, ensuring that all required files and paths are properly specified. Additionally, updating Atmel Studio to the latest version or reinstalling it might also help resolve any compatibility issues with Windows 10.