A: Try subsetting the drillhole data (ie. turning off a number of drillholes/sample points in the Attribute Manager) to less than 40,000 visible points and then see if the icon becomes active. If so, open the 3D spatial window and then turn on the visibility for the other data points. There is a data limit set for the number of points that is preventing all of the data being able to be opened into the 3D plot window initially so the workaround is to only open a small number of data points first of all. This solution can only be used in ioGAS version 6.3.1 and older.
In version 7.0 of ioGAS, you will need to create a subset of the file in Excel (i.e. to be less than 40,000 rows), and open the file in ioGAS. Once the file is loaded, open a 3D Attribute Map and use the Append tool to bring in the rest of the file. This workaround is only valid for version 7.0 of ioGAS.