I have pre-existing Excel spreadhsheets (see attached) that I am attempting to open, modify, save, and then present to the user in Excel 2016.  Here is the code I am running the workbooks through...  It attempts to added additional sheets to the workbook as needed..by copying a sheet called "Template".  I have a attached two spreadsheets.  One before going through the code, one after going through the code.  You can look at the Data sheet and the InventoryGroupData sheets to see what I am talking about.   Any ideas as to why this is breaking?

public bool OpenExcelWorkbook(
ReportData.OutputDataDataTable p_ExcelDataTab,
int p_BracketID,
int p_Year,
string p_SubmitType,
string p_UOM,
string p_WorkBookName)
{
Workbook ExcelWorkbook = new Workbook (WorkbookFormat.Excel2007MacroEnabled);

var Bracket = context.tblBrackets.FirstOrDefault(b => b.BracketID == p_BracketID);
var GroupsList = context.tblGroups.Where(g => g.tblBrackets.BracketID == p_BracketID);

FileStream stream = File.OpenRead(p_WorkBookName);
ExcelWorkbook = Workbook.Load(stream);
stream.Close();

bool SheetFound = false;
Worksheet ExistingWorkSheet = null;
Worksheet ParameterWorkSheet = null;
Worksheet CurrentGroupSheet = null;

foreach (tblGroup CurrentGroup in GroupsList)
{
if (!CurrentGroup.tblProdCodes.Any()) continue;

string GroupName = CurrentGroup.Group.ToString().Trim();
SheetFound = false;

try
{
ExistingWorkSheet = ExcelWorkbook.Worksheets[GroupName];
if (ExistingWorkSheet != null)
{
SheetFound = true;
}
}
catch
{
SheetFound = false;
}

if(!SheetFound)
{
Worksheet BlankSheet = ExcelWorkbook.Worksheets.Add(GroupName);
CopyTemplateToNewWorksheet("Template", BlankSheet, ExcelWorkbook);
CurrentGroupSheet = ExcelWorkbook.Worksheets[GroupName];
CurrentGroupSheet.MoveToIndex(0);
}

CurrentGroupSheet = ExcelWorkbook.Worksheets[GroupName];
CurrentGroupSheet.Rows[2].Cells[4].Value = "Group ID";
CurrentGroupSheet.Rows[2].Cells[6].Value = CurrentGroup.GroupID;
}

List SheetsToRemove = new List();
foreach(Worksheet cs in ExcelWorkbook.Worksheets)
{
bool IsCurrentGroup = GroupsList.Where(y => y.Group == cs.Name).Any();
if(!IsCurrentGroup)
{
string CellValue = cs.Rows[2].Cells[4].Value != null ? cs.Rows[2].Cells[4].Value.ToString().Trim() : string.Empty;
if (CellValue == "GroupID")
{
SheetsToRemove.Add(cs.Name);
}
}
}

foreach(string SheetName in SheetsToRemove)
{
ExcelWorkbook.Worksheets.Remove(ExcelWorkbook.Worksheets[SheetName]);
}

ParameterWorkSheet = ExcelWorkbook.Worksheets["Parameters"];
ParameterWorkSheet.Rows[1].Cells[1].Value = p_BracketID;
ParameterWorkSheet.Rows[2].Cells[1].Value = p_Year - 1;
ParameterWorkSheet.Rows[3].Cells[1].Value = p_Year;
ParameterWorkSheet.Rows[4].Cells[1].Value = p_UOM;
ParameterWorkSheet.Rows[5].Cells[1].Value = p_SubmitType;

ExcelWorkbook.Save(p_WorkBookName);

return true;
}

private void CopyTemplateToNewWorksheet (string p_TemplateName, Worksheet p_NewWorksheet, Workbook p_CurrentWorkbook)
{
Worksheet TemplateWorkSheet = p_CurrentWorkbook.Worksheets[p_TemplateName];

foreach(WorksheetColumn sc in TemplateWorkSheet.Columns)
{
WorksheetColumn dc = p_NewWorksheet.Columns[sc.Index];
dc.CellFormat.SetFormatting(CreateFormatCopy(p_CurrentWorkbook, sc.CellFormat));
dc.Width = sc.Width;
dc.Hidden = sc.Hidden;
}

foreach (WorksheetRow sr in TemplateWorkSheet.Rows)
{
WorksheetRow dr = p_NewWorksheet.Rows[sr.Index];
dr.CellFormat.SetFormatting(CreateFormatCopy(p_CurrentWorkbook, sr.CellFormat));
dr.Height = sr.Height;
dr.Hidden = sr.Hidden;

foreach (WorksheetCell scell in sr.Cells)
{
WorksheetCell dcell = dr.Cells[scell.ColumnIndex];
dcell.CellFormat.SetFormatting(CreateFormatCopy(p_CurrentWorkbook, scell.CellFormat));
dcell.Value = scell.Value;
}
}
return;
}

static IWorksheetCellFormat CreateFormatCopy(Workbook workbook, IWorksheetCellFormat sourceCellFormat)
{
IWorksheetCellFormat copy = workbook.CreateNewWorksheetCellFormat();
copy.SetFormatting(sourceCellFormat);
return copy;
}