This is possibly the result of two user accounts. Please send in a support ticket showing us the Ad ID# of your ad that you can not access...we can identify the account from the Ad ID.

The other cause could be a pop-up blocker in your browser.  Some browsers have it integrated and it is on by default.  You'll need to research your browser settings and turn off pop-up blocking if you can't see your ads in the Account Management area.