If you have forgotten your password, you can use the Microsoft Authenticator application on your mobile device to reset your password.
Open the Authenticator app on your mobile device.
Tap on the account you wish to change the password.
Tap on Change password.
The password change wizard will launch.
Pick the account to change the password.
At the Enter password screen, tap on Forgot my password.
Confirm the email or Username entry is correct.
Type in the Catcha characters and tap Next.
At the Get back into your account screen, select "I forgot my password" and tap Next.
At verification step 1 return to your Authenticator app, record the One-time password code (OTP).
Return to the password change screen and type in the One-time password code (OTP) and tap Next.
Enter and confirm your new password and tap Finish.
Your password will be reset and you can access Office 365 again.