The first thing that you will want to try is to right-click Presence in the Browser window and choose "Refresh." This will refresh the presets if they are installed correctly.
If that does not resolve your issue, you will need to check where you have your PreSonus Sound Sets installed. By default, they are installed into Documents>Studio One>Sound Sets. This option is set in Studio One under Studio One>Options (Preferences on Mac)>Locations>Sound Sets. Make sure that everything is in the right place and that you have the right directory listed.
If the issue persists, go into your Sound Sets folder and double-click one of your Sound Sets.
If all else fails, try removing your settings files from the program and re-configure.
Go to Help>Open Settings folder.
Copy the contents of the folder over to a folder on your desktop.
Close S1 and delete the contents of the settings folder with the exception of the user.license file as well as the "Extensions" folder.
Open S1 and go to Studio One>Options (Preferences on a Mac) to reconfigure your settings.
Test to see if the problem is resolved. If it is not, please feel free to copy your settings files back over from the backup that you created in step 2.
*If you are missing presets or Sound Sets after doing this, simply double-click one of your Sound Sets under Documents>Studio One>Sound Sets.