The main reason Starfield early access might not be showing or playable on Steam (particularly if you have the Digital Premium Edition) is that the game needs to finish downloading and unpacking its files, which can take some time after the initial download. Additionally, Steam sometimes needs to be fully closed and restarted to refresh the game status and enable the "Play" button. Key points to fix or understand why early access is not showing on Steam:

• Starfield's early access officially starts at midnight UTC on September 1, 2023, but Steam will show the official full release date (September 6, 2023) in its game page. This is normal and does not affect your early access rights if you purchased the Premium Edition.
• After preloading, Steam must unpack game files which uses disk activity; during this time the game might still appear unavailable.
• Completely exit Steam (including background processes) and then reopen Steam to refresh the game status so the "Play" button activates.
• Waiting some time for this process is necessary, especially considering system speed and drive performance.
• Some users found that restarting their PC or reinstalling the premium content can also help resolve launch issues.

In summary, if Starfield early access isn't showing or the play button is greyed out on Steam, it usually means the files are still unpacking or Steam has not refreshed properly. Closing and restarting Steam fully, ensuring the game has finished unpacking, and verifying you have the Premium Edition are the main steps to resolve this issue.