To parse an .xls file in Pega when the standard activity fails, you must first import the ADK File Parsing utility from the Pega Marketplace. Once installed, configure your parsing activity by setting a local variable to reference the uploaded file and creating a second variable that renames the extension to .xlsx. You then invoke the @ConvertXLSToXLSX function to transform the legacy format into a compatible modern file. Finally, execute the pxParseExcelFile activity using an .xlsx template to successfully process the data. This conversion bridge ensures the system can read older Excel formats without custom Java code.