Fixed the problem:
I had the exact same issue after purchasing recently, also with the FlyJSim 727. Here is a quick, and so far permanent, fix:
Go to your MacOS security and privacy settings
Go to the 'privacy' tab
Scroll down to 'accessibility'
Under 'allow apps to make changes', find X-Plane, and check the box.
NOTE - you may need to click the padlock in the bottom left and enter your password to allow changes.