After May 8, 2017. For those schools that are participating in Stand-Alone Field Testing (SAFT) on Computers (CBT), the "Welcome to Nextera" emails that provide Nextera Admin login credentials are slated to be sent to District Test Coordinators (DTCs) on Monday, May 8th.
You can find the complete CBT scheduele on CBT Support, visit: CBT Timeline: Significant Events article page.
All schools should be reviewing their test coordinator (District Test Coordinator, DTC, or School Test Coordinator, STC) information in SEDREF. If your school needs to update the test coordinator, visit How do I change the District Test Coordinator for my district article page to follow the "school letterhead" process.
(You can find this article is also in the Nextera Admin FAQ section.)