One of the common reason is if you leave a lot of blank lines in your calculator spreadsheet you may find that not all the options are seen. In order for your calculator to work properly just remove the redundant blank lines and you will be able to see all the options. There can be other reasons as well and may require investigation.
Another reason is if you have certain combination in the calculator spreadsheet that you don't want user to select as these combinations are not available, you tend to delete the grid parameters that are not available. This is an incorrect action because when you delete any grid parameter it disturbs the functionality of calculator. If you want your calculator to work properly and don't want your user to order for certain combination, do not delete the combination, just replace the it with the combination that you can provide.
For an example: if you have a calculator with two Grid Parameters: 1) Type and 2) size. In Type you have A B C and in Size you have X Y Z. Now the normal grid parameter that will show up in calculator will show up as Follows:
Now Suppose if you want your user to order the combination of Type A and Size Z, rather than deleting the parameter replace it with the combination that you want your user to see.