Error launching game: A different game is currently in session. Please come back later

Looking at the forum threads posted before, seems like a rare bug. Not sure if my situation applies as well:

I just finished running a session and have logged out of the game. A player is still in there mucking around and I can’t launch another game to prep.

Not sure if my situation is a bug or a feature?

You can boot them from the game by stopping the world server and then you can start your other world. (or send them a message asking them to leave the world).

That’s always an option. So is this working as intended then?

So If I’m running one game, players can’t join the others? I always thought that it was marketed as always available 24/7 for anyone to join

You can only have 1 world open to your players at any time (per Foundry License).
On the Story Teller tier, if you enable the game manger, it will automatically spin up the server that your players want to access - but still only 1 world active per license. As soon as players leave, all worlds will automatically be open (edit: and available 24/7 for anyone to join), but as soon as a player joins one, all other worlds will be locked out. This is part of Foundry’s terms and conditions.

Usually if you only have a couple of games running, 1 license is enough, as it is not often that all of your players will want to access at the same time.

If you require multiple worlds open often, then you will need to purchase a 2nd license from Foundry and add that to your Forge account.

Note that, as Mushie alluded to this is Forge respecting the FoundryVTT licensing terms.