alt+f not functioning

Hi, I am new with AutoIT and has developed coupled of test cases for PLM application performance.

My issue is application Alt+F is not working, when  press Alt+F it wont work some problem is there with application code.

but after pressing "Alt" and realeasing it the File menu get activated , and then if I press F key file menu  option get opened / appear in drop down.

THis is how i am trying to
end("!f") ;ALT+f (file)
Sleep(500)
Send("{DOWN " & $mnuOpenNX & "}");Down arrow # times to select Open In NX
Sleep(500)
Send("{ENTER}")   ;Press Enter

Even i am trying  this way...since ALT+V is opening so i was trying to use alt+V an dthen left arrow key 2 times since it is 3rd no from file menu.

end("!v") ;ALT+V (View)
Sleep(500)
Send("{LEFT}");Left arrow 2 time to select the File menu
Sleep(500)
Send("{DOWN " & $mnuOpenNX & "}");Down arrow # times to select Open In NX
Sleep(500)
Send("{ENTER}")   ;Press Enter



Help appreciated.

Thanks,
Sandip