Hi,
There's likely one of two things happening.
The first would be that you are using the login boxes in the center, which only work during activation. You need to log out and then log back in using the fields in the upper right corner. You need to use the email address you used during the account creation as well.
The second would be that when you reset the password, you either did not use at least 8 characters, or when you are inputting it, you entered it without remembering that it's case sensitive. If you used any upper case letters when creating it, you need to do that every time. Another frequent issue is resetting the password and using the same one, which blanks the field and means you have to reset it again,using a new password.
Let us know if this works or not.