If things don't go as planned, there will be a possible backup date for October 2nd. After careful consideration of several logistical topics, the agency decided on a later date for the launch.
The Artemis I mission will use NASA's Space Launch System megarocket to propel an uncrewed capsule around the Moon as part of the agency's push to bring humans back to the lunar surface. The second attempt on September 3rd was aborted after the Artemis I team detected a hydrogen leak that they couldn't fix.
NASA is preparing to make things run smoothly. Engineers will be testing the quick connect on September 21st to see if it works under the conditions required for a launch.
There is a question of whether NASA will have to test the batteries in the rocket's flight terminated system, which the Space Force can use to destroy the rocket if something goes wrong during its flight. It would take hours for NASA to roll the SLS back into the vehicle assembly building. The Space Force has the final say on whether or not NASA can go ahead without testing. The rocket's certification was extended by NASA from 20 to 25 days, but Space Force is still deciding whether to grant another extension.
NASA continues to respect the Eastern Range's process for review of the agency's request for an extension of the current testing requirement for the flight terminated system. Should the request be approved, the agency is continuing to prepare for the demonstration test.
NASA will attempt to launch the rocket on September 27th if everything goes according to plan. The launch date is sandwiched in between two other major space events, with NASA scheduled to send a spacecraft crashing into an asteroid as part of its Double Asteroid Redirect (DART) mission on September 26th.