How do I make an immobile camera? (Remake)

It is most likely your placement of the script. Instead, try placing the script inside of a LocalScript, which should be inside StarterGui (for example).

Do repeat wait() until game.Players.LocalPlayer.Character to wait for the character to load.

Next you'll want to get the camera, which is as simple as local cam = game.Workspace.CurrentCamera. Now you can add what you've done, with some small modifications...

-- after the lines explained above
cam.CameraSubject = game.Workspace.Part
cam.CameraType = Enum.CameraType.Attach

Notice the use of an Enum instead of a string. Usually it ensures it'll work. Plus it gives you a neat list of options to look at.

To prevent it from moving, however, I'd do this:

cam.CameraSubject = game.Workspace.Part
cam.CameraType = Enum.CameraType.Scriptable

cam.CoordinateFrame = CFrame.new(game.Workspace.Part.Position)

This will make it look forward. To rotate it, you can make the last line cam.CoordinateFrame = CFrame.new(game.Workspace.Part.Position) * CFrame.Angles(-x in radians-, -y in radians-, -z in radians-) OR you can add an argument to CFrame.new. This second argument will make the camera look towards that Vector3, so like cam.CoordinateFrame = CFrame.new(game.Workspace.Part.Position, -look at Vector3-)