I have the same issue. I reinstalled GSX multiple times together with Simconnect, VB2005,2012 and 2015.
When I start P3D I see that Couatl.exe is in the task manager but as soon as I click to load the scenery it disappears. Then when I click on add-ons in P3D I only see the addon manager. GSX is in trial mode and I tried to activate GSX but it says that the couatl scripting engine hasn't been started. Even though I made an exception in my AV and turned it completely off during the installation of GSX.
I hope you could help me.