According to Microsoft, there could be many reasons why you are not able to log into your Hotmail account. First double check to make sure you are using the correct password. Check that your caps lock button is off, as passwords are case-sensitive.
If your password is right, then the problem could be on Hotmail's end. Check the service status on the company's website. If it's green and you are still not able to log into Hotmail, someone may have hacked your account, in which case you will need to change the password.
It is also possible that your Hotmail account has been temporarily blocked due to unusual activity. You may require a support-assisted unblock that can take 24 hours or longer. A link on the bottom of the "Outlook.com Account Help" page will take you to a support page where you will need to enter some information into a form. A Microsoft customer service representative will contact you via email, either with instructions on how to unblock your account or requesting further info.
Be sure to refresh your browser by pressing "Ctrl" and "F5" on your keyboard at the same time. Clear the temporary cache and cookies on your browser to make sure you have the most recent version of the web page. Keep in mind your Microsoft Hotmail account will be closed after 365 days of no activity. Contact Microsoft Customer Support should none of these options work.