Welcome to Mobiflight ( Und Servus nach München
Sounds like a connecting Problem..... Badly i can not test on your computer to find the issue directly.
Some basic facts:
1. Simulator and Mobiflight should not run in a "Secured" Folder like "/Programmfilesx86 " etc. It is always recommend to install all Stuff in "own" folders.... Much better in a own partion of a harddisc or in best way on a own SSD Drive (indipendent from the Windows System)
2. Admin Mode is not basicly recommend by Sebastian and Mobiflight.... But Myself i run all Programms ( Whatever my Firefox Explorer, too) always in Admin Mode. Have never Problems with it.
Important: Your Mobiflight and your SIM must be in same Status.... If one is ADMIN then the other must be ADMIN, too.... Or Both should be non Admin. Just get sure you not mix it.
I not read somethin about you "Update" your FSUIPC. Please get newest version from http://www.schiratti.com/dowson.html
(V 4.971 at current moment Nov2018)
4. Try to change your sequence while starting: Maby the problem is you start MF before the Sim.... Simply start for testing Sim in front of Mobiflight.
Please report experience!
You said you have TWO FSX-SE installations on your system. "Maby" this also can create a problem. Get sure your FSUIPC is in correct Simulator.... Or maby delete the not used one.