In order to perform vertical transforms (other than Vertical Offset or local Ellipsoid Height transformations), you must first have the appropriate grid shift files. You can download these files directly from the Blue Marble Geographics website, under the Geographic Calculator download page (www.bluemarblegeo.com).
Most of these are self-installing files and by default they will install to the data path directory C:\ProgramData\Blue Marble Geographics\Geographic Calculator x64\DataSource\shiftfiles\vertical directory.
If the vertical grid shift files can not be automatically downloaded, they will need to be manually added to the install in the data path directory. This can be set under Preferences> File Locations.
For more information see Downloading Missing Shift Files
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