There was an issue in earlier versions of Golden Software products that the program subtracted 32 from the number of the symbol for all symbol sets except the default (GSI Default Symbols). So if you wanted to plot symbol 9 of GSI Map Symbols using a worksheet column, you would actually type "GSI Map Symbols:41" in the cell. This was fixed in MapViewer 8, so "GSI Map Symbols:41" refers to symbol 41. The GSI Map Symbols symbol set only has 30 symbols (indexed from 0 to 29), so if your file is a MapViewer 7 file, any cells calling symbol 30 or higher will plot an empty symbol on the map, so it will look like the symbol has disappeared. This 'disappearing act' will happen as soon as your map is updated (so once you've changed something like the maximum symbol size). To fix this, subtract 32 from each of your symbol numbers in the worksheet.
Updated October 6, 2016