The Excel _xlfn. prefix indicates that your workbook contains a function that is not supported by your version of Excel.
This is a common error you many receive, especially is someone sends you a spreadsheet. Most corporate computers do not contain the most recent version of Excel.
Unfortunately, if you see this error, the workbook will not work correctly. You can obviously rewrite the formula with something compatible.
Here are list of Functions not supported in Versions earlier than Excel 2007
Function not supported in Excel versions in 2019