Have you created the file using your current Excel version or is it an 'old' file that you are now opening with your current Excel version?
Might be a conversion issue. So try to recreate your workbook.
In case that fails. The following code will change all cells to number format with 2 decimals on all sheets upon opening your workbook. First you need to implement the code, save your workbook and then re-open to see the result.
Private Sub Workbook_Open()
Dim ws As Worksheet
For Each ws In Worksheets
.Cells.NumberFormat = "0.00"
Code needs to be placed under ThisWorkbook:
Hopefully this will solve/help with your unusual query.