Hello,
First excuse me for my bad english.
I have a same problem with FSX, FSUIPC and other addon.
After a lot of test, with an other developer, we find a solution. We are desactived McAfee version 10, and the addon menu work correctly.
Mcafee block the SimConnect.dll. SimConnect_Open returns E_FAIL whatever you do.
Now I change McAfee by AVAST Familly. This is a free antivirus.
Bye bye
Galaag