If you find yourself encountering an error saying, The 2K Sports Server is not available at this time. Please try again later, after attempting to accept the NBA 2K Terms of Service, then you may have submitted an unverified email address for your account upon creation.
This is a relatively easy fix! Just be sure to apply an email address that can receive and accept email verifications when creating your account. Once you've applied the correct email, you can also verify your account by using your platform ID to log into NBA2K.com.
This should resolve the error and allow you to complete accepting the terms.