Scheduled startup not working on macOs Tahoe

that’s a common one since macOS Tahoe quietly phased out the old Energy Saver scheduling UI.

The terminal command you used is fine, but it often fails when FileVault is enabled, because the system can’t complete the boot until the disk is unlocked manually. Either disable FileVault under System Settings > Privacy & Security > FileVault, or skip the startup scheduling and use OnyX instead, it still exposes that functionality cleanly. After running your pmset command, double-check it’s actually saved with pmset -g sched. If it’s blank, the schedule didn’t stick.

It may be that FileVault is enabled. If the Mac powers on but you don’t decrypt the drive, it will power down after a few minutes. The setup assistant for Tahoe enables FileVault. If you don’t need it, turn it off in Security & Privacy System Settings.

Did you verify the schedule was written?

pmset -g sched

Terminal should still work but why bother. Download the free app "Onyx" which has a utility for programing the startup/shutdown feature. Works great. I use on all my macs.

or skip the startup scheduling and use OnyX instead, it still exposes that functionality cleanly.

OnyX doesn't create its own schedule, it just provides a GUI that runs the appropriate pmset command (like the macOS GUI did previously). Nothing will be any different using OnyX to set up the schedule.