There is a very simple way to check.
In the top of steam click on tab which I think it called general sorry can't check right now.
If you can't find it click on the tabs on the top until your find the drop down tab called "Settings" this is where you general setting will be found, when you click on settings you will see a screen pop up which will say the current stats of your steam guard. It is it offline there should be a option to help you get it online.
Sorry for not remembering the tab but it is the main one.
Hope this helps!