Unfortunately the best we can manage with UPS is a very general ground quote based on zip codes and weight, our cart is unable to account for things that UPS asks for like package dimensions or the buyer's specific address (which we will not know until the order is complete). Depending on your circumstances it may be better to declare your costs by other means if you will be shipping with UPS.



You may be able to continue using packaging costs for this particular item, for example if you assign it to a Large Box and set the cost of that package to match your average shipping cost with UPS you will able to easily cover your costs for this particular item without changing any of your other settings.



If you ever need to add another additional charge for international shipping or shipping to more expensive locations outside the continental US then you can also augment your packaging costs by adding a few shipping rules. For example you can create a rule for a flat rate of $0 for domestic orders which adds nothing on top of your package costs, and a rule for other countries that is based on weight or just a higher flat amount to account for extra costs shipping long distances.

In the product settings for the item that ships in a USPS flat-rate box, specify a shipping weight of 0.00 and select a Package Type that you will only use for that product, with a Capacity indicating how many units of that product can be shipped within that flat rate. Then in your Cart Shipping Settings, set that flat rate as the Cost of the Package Type you use for that product, but leave the package Weight at 0.00. Leaving the product and package weight sttings at 0.00 will exclude this item from any UPS/USPS rate lookups.



For the other item that ships by UPS, you could just use the same method as above to define a different nationwide flat rate, which you'd simply assign as the Cost for a different Package Type you only use for this product. However, if you prefer to have us perform a UPS Ground rate lookup for this item, be sure you specify an accurate per-unit Weight in the product's settings, select a different Package Type than your other product, and leave the empty Weight of that Package Type at 0.00 (or enter the empty weight of the container itself) in your Cart Shipping Settings. If the standard UPS Ground rate we obtain from UPS for this item is insufficient (e.g., because the item is oversize/overweight for basic UPS Ground service), you may wish to also specify a Cost for this item's Package Type that would be added as a flat surcharge on top of the base UPS Ground rate we obtain.



It appears you've deleted any shipping rules you may have previously set up, so I can't tell the reason for the shipping -error- you mentioned anymore, but that -error- would indicate the buyer's cart order does not qualify for any shipping rules you have set up.

Unfortunately, due to the unusual way you have this set up, ordering both items would indeed mess up the UPS rate lookup, as that would be obtaining a rate for the total order weight distributed across 2 (or more) separate parcels, rather than only counting the 40-lb. item(s) as UPS-shippable parcels and disregarding the other product entirely.

Unfortunately, due to the unusual way you have this set up, it's true that ordering both items would indeed mess up the UPS rate lookup, as that would be obtaining a rate for the total order weight distributed across 2 (or more) separate parcels, rather than only counting the 40-lb. item(s) as UPS-shippable parcels and disregarding the other product entirely.