Cause
An Excel file format or table that contains more than 64'000 cells is being exported and the "Create cell names" box is checked. Cell names exceeding 64'000 will not be created. Excel does not allow more than 64'000 cell names.
Solutions
If the cell names are not required, uncheck the "Create cell names" option in the Export file to Excel tab, or else, ignore the error message.
If, on the contrary, cell names are to be used when exporting a file, uncheck the tables unnecessary to your export in the Include Tab dialog (such as Accounts (Base).