We should not let the "64-bit" part throw us off. Power BI has trouble working with xls files. We need to save the workbook as an xlsx file and try again.
Power BI can also work with XLS files. a different mechanism is used by power BI to read them than XLSX files, however, so you need to download and install the ACE provider from the link it gives you
Also, enroll in Power BI course to become proficient in this BI tool and clear Power BI certification exam.