Emergency off and the marker file

The page only shows when all three of these are true:

Switch on is Yes.
The marker file plugins/system/easycomingsoon/ecs-active.txt exists.
The switch-off time (if set) hasn't passed.

If you're locked out:

Emergency link: open the emergency link shown in the Dashboard's Emergency off card, and bookmark it. It looks like https://example.com/?ecs_off=YOUR-SECRET-TOKEN; the real token is unique to your site. Keep it private. The link sets Switch on to No and deletes the marker file, so to turn the page back on, click Re-create marker file on the Dashboard and set Switch on back to Yes. Regenerate secret on the Dashboard replaces the link.
FTP / file manager: delete plugins/system/easycomingsoon/ecs-active.txt. The page turns off immediately. Switch on still says Yes in the settings.

Turning the page back on. Whether the marker was deleted by FTP or by the emergency link (which also deletes it), click Re-create marker file in the Dashboard's Emergency off card. If you used the emergency link, also set Switch on back to Yes. The card shows whether the marker is present or missing.

Note: Saving Options does not re-create the marker file. Even with Switch on set to Yes, the page stays off until you click Re-create marker file (installing or updating the package also re-creates it).