AmericanHero, as you may have seen elsewhere in the forums the User Authentication Failures encountered by some Players stems from an update to our system yesterday afternoon. We have since identified the source of the error, and are working to eliminate it entirely to avoid affecting Customers (yourself included) again in the future. I adjusted your account so you are once again able to log in. If you or others feel you have an account encountering 'User Authentication Failure' in error, please don't hesitate to contact us through Chat or submit a Support Ticket at https://tera-support.enmasse.com/.
Sorry for the interruption, you are now free to continue with your Hero business.