Read some of the 30+ threads already started on this.

Have you bothered to look at any of the previous dozen or so posts,  under technical issues.

When you went to start this post, did you notice any other posts advised that might relate to your question.

Clear all cookies, history and cached data. Then click Sign out and click F5 a couple of times .
That will sign you out.

Why are'nt the dozens of posts (and answers  and suggestions) on this enough already?