What do you mean by "missing"?
Missing means Instead of values it is displaying only ZEROS.
The problem you are experiencing is due to 1 of 2 causes. Both causes are due to how Tableau's subtotals and grand totals are separately computed at a coarser level of detail than the detail cells so when it comes to table calculations that depend on a certain level of detail (that is found in your detail cells) when they are computed in the grand totals they not have the needed level of detail. Check out the posts at Grand Totals and Subtotals | Drawing with Numbers for more details on this.
The 2 possible causes are:
1) The addressing (compute using) of the table calculation is not properly set so it's not addressing on the needed dimensions for the Grand Total. For example it might need to be Table (Across) instead of Table (Down), or compute on specific dimensions in a certain order, etc. Without seeing your view (ideally a Tableau packaged workbook with some sample data representing your problem) we can't give you more details.
2) There simply isn't enough detail in the Grand Totals to accurately get the results that you need...in that case we need to change how the view is set up. Sometimes we can work around that using a combination of row-level and aggregate calculations, sometimes we need to add dimension(s) to the Level of Detail shelf to increase the grand total LOD (GTLOD) and then use table calculations to deal with the increased LOD. Again, without seeing your view I can't give you much more details than that.