Please see the combined screenshot beneath. The left states: "Most sunrise reservations will be available up to 2 months ahead of time." But the right alleges "Not Yet Released", but I am posting this on 1/16/2019, which is obviously within 2 months of 2/11/2019.
Is the federal gov't shutdown the snag?
Your own linked page has the answer/alert at the very top:
During the federal government shutdown, this website will not be updated and may not reflect current conditions. Some national parks may remain accessible to visitors; however, access may change without notice. Some parks are closed completely. Some visitor services may be available when provided by concessioners or other entities. For most parks, there will be no National Park Service-provided visitor services, such as restrooms, trash collection, facilities, or road maintenance. For more information, see www.doi.gov/shutdown and the park website.