I am using ArcGIS 10.5. I often export tables to excel files and am wondering why the files are created are XLS files instead of the XLSX file type? I've started using ArcGIS Insights and it will only accept a XLSX file. I can easily open Excel and create the XLSX file type by saving a new file, but why doesn't ArcMap create XLSX files in 10.5. Am I missing something here? Seems strange ArcMap won't create the XLSX file type and Insights will only import an Excel file as a XLSX file type.