You might want to click on the down arrow on the home tab on the top
left. Then click on Account settings. Then on the next screen look on
the upper left and click on security. You will see two lines, one is
Login Notifications and the other is Login Approval. If these are on
then you will be challenged each time you log in from another computer.

I hope this is the problem, otherwise I have you barking up the wrong tree.