Email will not launch

When I click on "email," the homepage simply reloads. When I click on "view inbox," the following error is presented: "http error 400: problem accessing /service/preauth. Reason: authentication failed for [my username]." I've used two browsers Chrome (version 39.0.2171.65 m) and IE (version 11.0.9600.17358). This happened a month ago, too, and I _still_ can't access it.