In the United States, all electronic devices that use certain wireless radio transmissions, including cellular, Wi-Fi, Bluetooth, and other standards and frequencies, must be approved by the Federal Communications Commission. It's technically illegal for retailers to sell devices that haven't been approved, which is probably why Google had to rapidly remove the Nexus Player pre-order status from the Play Store on Friday. But now the results of the FCC's tests on the Player have been posted to the Commission website.
Barring any violation of FCC rules and standards on the part of manufacturer ASUS, which is unlikely in the extreme, the Nexus Player is either approved now or will be soon. That means that Google should be re-enabling pre-orders on the Play Store in a matter of days. At the time of writing, Google's first retail Android TV device is still marked as "out of inventory" on the Play Store with the disclaimer that it hasn't been approved by the FCC. The same is true for the console-style Bluetooth wireless controller, though if there's an entry for the controller in the FCC's web database, we haven't found one.
Usually wireless devices are submitted for FCC certification weeks or even months ahead of a retail launch, but the cover letters for ASUS' Nexus Player application are marked "October 7th." Even so, the FCC's official date of receipt is October 18th; it's possible that ASUS shipped a final retail unit from its Taiwanese headquarters, as indicated by the contact information.
All this boils down to the following: the Nexus Player should be available for pre-order (or even purchase) again very soon.