get (activekeyboardmodifier) and Secure Keyboard Entry FYI

This is an FYI / answered-question posted as a service to future searchers who may encounter this issue:

I had a problem where FM Pro 13 ( though this would apply to any version of Filemaker on the Mac) would not recognize keyboard modifier keys (option, Shift, command, control) when a Get (ActiveKeyboardModifierKeys) script step was called.

I was quite puzzled until I happened across this StackExchange thread on Mac OS X Secure Keyboard Entry. This is an OS-level feature that can prevent any app from receiving the full range of keyboard input from the OS.

In my case, 1Password's Safari extension had enabled OS X Secure Keyboard Entry, thus preventing Filemaker Pro from receiving the modifier keys when they were pressed during script activation.

To fix the problem I simply quit out of Safari.

Note that in your case, the culprit app may be different; any app can invoke Secure Keyboard Entry; typically it's a password-management app but YMMV.