If you see a message saying that you have logged in too many times, it means that your previous session is still active. Click Continue to log in now. This will log you out of your previous session and allow you to access the site.
If you are aware of your previous session and don’t want to proceed then click Cancel to stop logging in.
Although unlikely, it is possible you have seen this message because someone else is using your login. Continue to log in, but you may like to change your password, just in case. To do this, click on your name at the top of the screen and under My profile, scroll down to Current Password. Enter your password and then your new password and click Save in the bottom-right corner.