Make sure you are using the raw HB utilities (not the rescaled, zero-centered diffs).
Sum the total utility for each of the alternatives in the simulator. Exponentiate the sums. (That means use =exp(U1), where U1 is the total utility for alternative 1, etc.
Normalize those exponentiated sums to sum to 100% within respondent.
Average those results across people.
If you are still having problems, you can email your spreadsheet to our technical support group and let them have a look to see where your mistake is.
My best guess is you are trying to use zero-centered diffs rescaled utilities rather than the raw utilities.