the second parameter to Raycast is a vector3 which should represent the direction you want the ray to travel in as a vector. Orientation returns the XYZ angles in degrees of the part, rather than its look direction
try this instead:
local mouse = game.Players.LocalPlayer:GetMouse()
local raycast = workspace:Raycast(workspace.CurrentCamera.CFrame.Position, (mouse.Hit.Position-workspace.CurrentCamera.CFrame.Position)*10)
print(raycast.Instance)
I just do that to add leniency to the raycast, because the second parameter uses the size of the vector to determine how far the raycast should reach, so if the raycast travels the exact distance there is a chance that it wont detect the part
it would probably still work without the *10