First, check your bookmark for the site. The url should start with "https" not "http". If it is missing the "s", edit your browser bookmark link to reflect this.
Then, if the issue is still occurring, it is typically a cookie issue. You should log out of H-M, then goto your browser settings, clear all cookies related to this site. I recommend closing your browser and then reopening and try logging back in to H-M.
Let us know how you do.