Garry's Mod servers, like most source game servers, require an AuthKey or 'GSLT Key' to run publicly. This is so that there is a layer of accountability for server owners to ensure that real people create them and to hold them accountable for any violations of the game's terms of service. There are multiple qualifications for generating a GSLT key; the user must not be banned or 'limited' and must have a registered phone. In addition, the user must own the game and have a cap of a thousand game server keys.
1. Open the Game Server Account Management page.
2. On the App ID of the base game field, enter 4000.
3. Add a memo to distinguish between tokens easily, then choose Create.
4. Copy the Login Token that appears; this is the GLST key.
5. Log in to the BisectHosting Starbase panel.
6. Stop the server.
7. Go to the Startup tab.
8. From the Workshop Authkey field, toggle the field On and paste the Login Token.
9. Start the server.