In some cases the preset files for the Electric Organ bank get installed without proper names. Therefore, MachFive can't load those presets. To fix this, navigate to your MachFive Sounds folder and go to 02-Electric Keyboards >>> Presets >>> 02-Electric Organ. Single-click on each preset, then single-click its name once again. This will allow you to edit the name of the file. For example, the first preset "Full Rock Organ A" should be changed to "Full Rock Organ A.M5p". Change the name of each preset in this folder to include ".M5p".
In order to activate this change, return to MachFive, click the MORE button below the Soundbank field, and choose "Rescan MachFive Soundbank."