Cellformat drawing right border works on one cell but not another

I have a header table in a word document (see attachment below), I had removed some cells and it has messed up my table border. The code below should work for both cells, but only one works.

'Re-draw right border
headerTable.Rows(3).Cells(3).CellFormat.Borders.Right.LineWidth = 2.25 <-- that workds
headerTable.Rows(4).Cells(1).CellFormat.Borders.Right.LineWidth = 2.25 <-- that didn't??

What can I do to make row 4, cell 1 set to with 2.25? I also tried doing RowFormat and that didn’t work either. Please help! Thanks!
P.S: Sorry I sent the example without data, but the cell that works doesn’t have any data but the cell that doesn’t have data…does that matter?

Hi
Thanks for your inquiry. Please try also setting LineStyle and color as shown in the following code:

headerTable.Rows(4).LastCell.CellFormat.Borders.Right.LineStyle = LineStyle.Single
headerTable.Rows(4).LastCell.CellFormat.Borders.Right.Color = Color.Black
headerTable.Rows(4).LastCell.CellFormat.Borders.Right.LineWidth = 2.25

Hope this helps.
Best regards.