An account lockout can happen if one enters their passwords 10 times incorrectly. After the 10th time a user will be given a capcha code to enter. After the 15th attempt, the account will be locked for 15 minutes. The user should be able to sign in after this 15 minute timeframe. If a user cannot remember their password, they may reset their password.
PennO365 passwords for faculty, students, and staff must be reset by changing the user's PennKey password here: https://weblogin.pennkey.upenn.edu/changeexpiredpassword. See the PennKey/KITE/PennO365 Password Sync Information accouncement for more information.