Looks like I got them working.
Ensure Orbx ObjectFlow 2 is enabled in the Prepar3D v4 Add-ons menu.
Hit 'Verify Files' on the Orbx Libraries in FTX Central 3 and it should force an update of about 500MB.
I'm faced with the same issue along with a friend. Clean install of v4.5.
I'll try to find a solution myself as none of the above has worked. I believe that it could be linked with ObjectFlow 2, however, I'm unsure.