When exporting the gift grid to Excel a temporary file is created.  This error is related to permission where the Excel file is being created, whether in the Files Folder or the user's local machine.

Verify that the path under User Options > File Locations, Excel Spreadsheets is referencing a valid location that the user has access to and the ability to write to that location.

If you do not have access to the specified path remove the path from the field and attempt to export again.  If you are still unable to export, Click Chat with Support and reference this article.