Shipping Rates now populating for US customers

[ryvolution]

About to launch my site soon and came across an issue when testing shipping options for US customers. 

I'm based in Canada and selling a coffee product. I've set up 2 levels of shipping A) Free shipping over $49; B) carrier and app calculated rates.

When testing, the Free Shipping option works but purchases under the free shipping threshold don't work. To eliminate the possibility of it being a "Carrier and app calculated rate" issue I tested it with a Canadian address and it works. Given that the "Carrier and app calculated rate" for Canada and the US is both provided by Canada Post I'm not sure this is the issue.

My second guess is that it could be Location related. I'll be fulfilling from my home for now, so I've entered that address but it says it can't be verified. Not sure if this is the bottleneck but I thought I would include this detail for completeness.

My last guess is that it could be product type related. I'm aware that Coffee products require additional documentation (FDA prior notification) to be shipped to the US, which will be included, so I'm not 100% sure if this is the issue either.