A build check error in the area "Bundling server.ts". An error: the game cannot be published until it is fixed.
The build check runs on every game LobbyLab builds, and each problem it finds has a stable code, the exact message, the file and line when it names one, and a link to this page.
What the check looks at
The check bundles server.ts with the sim kit into one module of at most 1.5 MB.
How to fix it
Import only names the sim kit exports; check the spelling of the name the message shows.
Import only names the sim kit exports, fix the build error the message shows, and keep the server small.
See also: every error code, the API reference and the docs.