The October demo black-screen advice
For the demo’s startup black screen, the official advice was to wait up to ten minutes. If the game still did not recover, players were directed to submit a support ticket.
That was advice for the demo issue, not a universal repair for every future launch failure.
First-launch shader compilation
The October 29 Early Access announcement described a shader-compilation screen for the first launch, along with fixes for some startup and login compatibility problems.
A shader-compilation screen makes the startup work visible. It does not establish that every black-screen problem has the same cause or that all launch failures are fixed.
If you still cannot start
Check your system against the PC requirements and use the official support destination linked from the ArcheAge Chronicles website.
Keep the demo advice and Early Access changes separate when describing your problem. Do not treat a planned fix as a machine-specific diagnosis.