First thing to check ... are you absolutely certain you are entering the correct password? If this is your first time trying to log in, it's easiest and most accurate to copy/paste your password from the email you should have received after submitting the registration form.
Each account is meant to be used by only one person. For security reasons, the same account (email & password) can not be used simultaneously in different browsers or on different machines. For example, if you log in on one machine, then a second person logs in with the same password on another machine, you will automatically be logged out.
Your browser must have cookies enabled to store the login info.
Your session will expire after 600 minutes of inactivity. This is to prevent other users from accessing your account if you forget to log out.
Are you getting the login prompt for every page?
If it appears that your password is accepted, but then you get the login page again
when you try to go to another page, it could be that your cookie file (where the
login data is stored) has somehow become corrupted. It can happen when your computer
experiences an unexpected shutdown such as from a power outage or fatal error, "blue screen", etc.
In order to determine if the cookie file is the culprit, you need to delete it.
Deleting the file doesn't hurt your login, and if it solves the problem then you know it was corrupt.
After deleting the cookie using the following directions,
you can return to the login page and hopefully the problem will be solved.
How To Delete the Cookie
Look for and delete the cookie named www.sijhsaa.bracketmaker.com using the
instructions at AboutCookies.org.