As explained, many times already on the forum, if you see the Couatl.exe running but not its menu, it's possible it has been stuck from a *previous* FSX session.
The reason for this is usually either relaunching FSX too quickly before allowing the Couatl.exe from the previous session to close OR another addon (we saw this with some 3rd party joystick drivers) in the EXE.XML, which is stalling Simconnect and prevents Couatl to get notification to close from FSX.
You can check if this is the case if, before you launch FSX, the task manager already shows a Couatl.exe running. In this case, just terminate it with Task Manager and then start FSX.