Macro works under Excel 2010 but not Excel 2013

I've got a macro I developed on my PC (Excel 2010/Windows 2010) for a client who has Excel 2013/Windows Server 2012.

On my PC, the macro correctly finds workbooks (e.g., 18BC1111.xlsx) in a folder. On her PC, the macro can't find those files.

The attached picture shows the code snippets (identical on both PC's) and the MsgBox that checks the filename and len(filename) in the folder.

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Thanks for your response saying that you needed the entire application. I've just uploaded all that information:

= Description of how it's supposed to work, in "TheBCarchiveMacro.pdf" READ THIS FIRST
= The macro-enabled workbook containing the macro: "BCarchive.xlsm"
= Two test files.

You should create two folders: Process (containing the two test files), and Archive (which will initially be empty), and then click the icon in "BCarchive.xlsm" to kick off the macro.

Again, the macro succeeds under Excel 2010/Windows 2010, but failed under Excel 2013/Windows-Server 2012

Thanks for your help.