Oh great. That’s a problem since the anniversary edition. Cause I can’t start the .air as administrator. Normaly it should work (and it worked right before the anniversary edition)…
Now it works! Here is how I did it (Maybe there were other possibilities, but that’s the fastest one I’ve found?):
Open your console (cmd) as admin.
Type:
net user administrator /active:yes
Switch to the “new” administrator user.
Install fflogs.air
Sign out the admin user, switch back to your “right one”.
Enjoy! (And you can deactivate your admin with “net user administrator /active:no”)
Maybe there where other ways to do it… 
Thanks for your tipp - I also google’d it and found thats because the admin privileges. But I didn’t believe, cause I got all privileges (and tried everything else which worked well…).