This means that the ‘BezierTween’ is either not accessible at ServerScriptService, or maybe it hasn’t loaded in yet and you are trying to call for it, or the module name itself is not ‘BezierTween’.
A fix if the module is in ServerScriptService and it’s name is ‘BezierTween’, then it’s a good chance the module is trying to be retrieved before it has been loaded.
Also make sure it ain’t a LocalScript since ServerScriptService can’t be accessed from a LocalScript
local BezierModule = game.ServerScriptService:WaitForChild("BezierTween")
local BezierTween = require(BezierModule)