If you attempt to log in and experience a long loading time with only a spinning circle and no page load, you are likely facing a cache and cookies issue. To resolve this, simply clear your cache and cookies, then refresh the page.
Full instructions for clearing cache and cookies for all major browsers can be found under the article:
How to Clear Cache and Cookies in the general section of the help centre
Note, you only need to clear your caching cookies. You do not have to clear your browsing history.