Excel to Table failing

I have an arcpy script that works on one machine, but fails very early on another.

import arcpy, os

arcpy.env.overwriteOutput = True

xlFile = r"D:GISmtdataExcelTable.xlsx"
outGDB = r"D:GISmtdataData.gdb"
arcpy.env.workspace = outGDB
mapTable= "xxExcelOutput"
inMemMapTable= r"in_memoryxxExcelOutput"

sheetName = r"Map Sheet"

arcpy.ExcelToTable_conversion(xlFile, inMemMapTable, sheetName)

It fails on the arcpy.ExcelToTable_conversion() with the following error message:

Traceback (most recent call last):
  File "D:GISmtreadexcel.py", line 13, in <module>
    arcpy.ExcelToTable_conversion(xlFile, inMemMapTable, sheetName)
  File "C:Program Files (x86)ArcGISDesktop10.5ArcPyarcpyconversion.py", line 60, in ExcelToTable
    retval = convertArcObjectToPythonObject(gp.ExcelToTable_conversion(*gp_fixargs((Input_Excel_File, Output_Table, Sheet), True)))
ExecuteError: 
Traceback (most recent call last):
  File "c:program files (x86)arcgisdesktop10.5ArcToolboxScriptsExcelToTable.py", line 252, in <module>
    arcpy.GetParameterAsText(2))
  File "c:program files (x86)arcgisdesktop10.5ArcToolboxScriptsExcelToTable.py", line 203, in excel_to_table
    out_fields = gen_out_fields(workbook, sheet, out_path, is_gdb)
  File "c:program files (x86)arcgisdesktop10.5ArcToolboxScriptsExcelToTable.py", line 175, in gen_out_fields
    out_fields.append(clsField(f, out_path, is_gdb, out_fields))
  File "c:program files (x86)arcgisdesktop10.5ArcToolboxScriptsExcelToTable.py", line 33, in __init__
    if not name[0].isalpha():
IndexError: string index out of range

Failed to execute (ExcelToTable).

The machine it works on is running 10.3.1, and it fails on 10.5. I thought maybe there was a change/difference in parameter requirements in 10.5, so in ArcMap I ran just the Excel to Table tool from ArcToolbox

and I get pretty much the same error:

Executing: ExcelToTable D:GISmtExcelTable.xlsx in_memoryxxExcelOutput "Map Sheet"
Start Time: Tue Mar 21 09:30:15 2017
Running script ExcelToTable...
Failed script ExcelToTable...

Traceback (most recent call last):
  File "c:program files (x86)arcgisdesktop10.5ArcToolboxScriptsExcelToTable.py", line 252, in <module>
    arcpy.GetParameterAsText(2))
  File "c:program files (x86)arcgisdesktop10.5ArcToolboxScriptsExcelToTable.py", line 203, in excel_to_table
    out_fields = gen_out_fields(workbook, sheet, out_path, is_gdb)
  File "c:program files (x86)arcgisdesktop10.5ArcToolboxScriptsExcelToTable.py", line 175, in gen_out_fields
    out_fields.append(clsField(f, out_path, is_gdb, out_fields))
  File "c:program files (x86)arcgisdesktop10.5ArcToolboxScriptsExcelToTable.py", line 33, in __init__
    if not name[0].isalpha():
IndexError: string index out of range

Failed to execute (ExcelToTable).
Failed at Tue Mar 21 09:30:16 2017 (Elapsed Time: 1.20 seconds)

What could be causing my arcpy to not be able to read my Excel file, and how do I fix it?

The Excel file was originally an export from Google Sheets, so I re-saved it in Excel with no effect. I removed spaces from the file name and the sheet name, also with no effect.

I created another Excel file with a similar filename and sheet name but with dummy data, and this has worked successfully, so I suspect now there’s something in my original file that the Excel to Table tool doesn’t like, but I am unsure what to look for, particularly because the exact same file works fine on another machine.