LTL minimum charges may explain why the freight quotes on your cart are checkout pages aren't fluctuating.
LTL freight carriers have a minimum charge which is the lowest price a carrier will offer its services for. The minimum, sometimes referred to as Absolute Minimum Charge (AMC) or Minimum Floor Charge, varies by carrier. The minimum is often not met until the shipment weight exceeds 500 pounds. Merchants sometimes mistakenly believe the LTL Freight Quotes product they have installed isn't working because the shipping rate displayed in the cart isn't changing. If you have this concern, perform additional tests with increasingly more weight until you begin seeing fluctuations in the shipping rate. The easiest way to do so is to keep increasing the quantity of the item in the cart.
If the weight of the cart exceeds 500 pounds and you still don't see a fluctuation in the shipping rates, open a support ticket by emailing firstname.lastname@example.org. In your email include a screenshot that contains the ship to address, the displayed shipping methods, and the cart contents.