Hi Ant,
I have seen this issue before, assuming that you have verified that the track is routed out to the Main output in the Console. You will want to remove your settings files from Studio One and re-configure. Here are instructions:
1. Go to Help>Open Settings folder.
2. Copy the contents of the folder over to a folder on your desktop.
3. Close S1 and delete the contents of the settings folder with the exception of the user.license file as well as the "Extensions" folder.
4. Open S1 and go to Studio One>Options (Preferences on a Mac) to reconfigure your settings.
5. 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.
If the problem persists, you will want to submit a support ticket from your my.presonus.com account. Just click on "Support."