The download is complete, yet the Play button still does not let you begin. If the game is in preload, that can be expected. Having the files on your drive and having permission to launch the released game are separate stages.
Valve’s Steamworks documentation explains that preloaded content remains encrypted on the player’s disk until release. Steam then decrypts it before it can be played. The feature’s availability depends on the title and release arrangement.
Read the offer’s exact wording
Preload is not the same as an opportunity to play before the main release. Steam’s Advance Access explanation describes that separate feature. A purchase page should establish what the selected edition actually includes; do not infer early play from an early download.
For a group planning launch night, record the official availability time and the applicable time zone. Check the platform and edition for each participant. A release arrangement on one storefront does not establish the schedule on another.
Leave room for the remaining work
A completed preload does not guarantee an instant start at the release minute. Decryption, updates and any required setup still have to finish. Valve also notes that preload updates can occupy additional disk space before they are applied.
Keep enough storage available according to the game’s current requirements and avoid deleting unfamiliar preload files to make the progress bar move faster. If the client reports a problem, use official support information rather than an unofficial “unlock” download.
A practical plan is to complete the available download, check the announced schedule and allow time for the client to finish release processing. Preloading can move substantial downloading earlier; it does not turn every remaining step into zero waiting time.