Unturned servers got an upgrade! Since version 3.21.31, servers need a special code (Game Server Login Token) to show up on the online list. This code also helps players keep track of their favorite servers even if the server address changes.
Setting up your own GSLTs
GSLTs can be created on Steamworks Dev Center.
You'll need to provide Unturned's app ID (304930) and a memo to remember which server the token is for.
Unturned game server configuration on ScalaCube
Now all you have to do is just go to the Server section of your ScalaCube control panel as show in the screenshot below.
You should now select the "Manage server" for the exact Unturned gameserver that you wish to be configured.
On the next page that pops up, click the "Manage" button on the desired server option.
In the menu that you can see on the left side, select the option "Settings", insert your newly created GSLT into the specific settings field.
Automating GSLTs
If that was too cumbersome, then you should know that Valve is also providing an IGameServersService online API to automatically manage GSLT tokens. You are free to check their documentation by following this link: https://partner.steamgames.com/doc/webapi/IGameServersService.
In case of any follow up question ScalaCube support will always be happy and eager to help answer.
Summary:
Setting up your own GSLTs
GSLTs can be created on Steamworks Dev Center.You'll need to provide Unturned's app ID (304930) and a memo to remember which server the token is for.
Unturned game server configuration on ScalaCube
Now all you have to do is just go to the Server section of your ScalaCube control panel as show in the screenshot below. 
You should now select the "Manage server" for the exact Unturned gameserver that you wish to be configured.
On the next page that pops up, click the "Manage" button on the desired server option.
In the menu that you can see on the left side, select the option "Settings", insert your newly created GSLT into the specific settings field.
Automating GSLTs
If that was too cumbersome, then you should know that Valve is also providing an IGameServersService online API to automatically manage GSLT tokens. You are free to check their documentation by following this link: https://partner.steamgames.com/doc/webapi/IGameServersService.In case of any follow up question ScalaCube support will always be happy and eager to help answer.
Summary:
- Servers page
- Manage server
- Manage
- Settings page
- GSLT field