It seems that http ends up with CloudFlare redirects so the gadget gets some redirect HTML instead of JSON. Use https - https://coinbase.com/api/v1/prices/buy which is where it ends up after redirects. Only "amount" is not conclusive as there are several amounts, but json.total.amount works fine. And make sure that you you clear your JSON keys for field 1, 2 and 3 (when they cannot be resolved final amount can't be calculated correctly as well).