Simply tap on “Forgot your password?” in the sign-in pop-up. Follow the instruction there to reset
If you created your HTC Account with email address, please make sure that you fill in the right email address and password. If you forgot your password, you could use “Reset your HTC Account password” link to reset your password.
If you created your HTC Account using your social account(facebook,Google, or Steam), please make sure that you signed in with the same social account.