I understand where you are coming from on the development side of it but their understanding is apparently very different. Regarding my configuration page for the TaxCloud plugin, when it comes to the zip code fields, mine are labeled as the Zip4 field first, followed by the Zip5 field. That is how they are labeled but if you actually enter the data that way you get a configuration error. I tried it just to make sure so that I could note it. On initial configuration of the plugin I filled the address data in as fast as possible based on the fact that we always know what goes where so I had the correct numbers entered. I didn't even really look at it until I was trying to figure out what may be causing my issues. When I noticed the labels were listed in backwards order (based on a typical zip code of course) I flipped the numbers to match the field labels and promptly received an "Invalid City" error that was created by the incorrect zip code numbers. The labeling is a small issue for those of us that complete our address data as we are used to. But, as I have previously said, if there are others who see their configuration page listed the way mine shows up and they actually read the entire list of field labels, they will most likely end up putting the wrong part of their zip code in those fields. I am sure I can find the error within the component files where I can correct this so not a big deal.
Regarding the configuration of the PayPal page, that is so simple and straight forward that it is impossible to screw that up. Here is how my test transaction went: I made a purchase of a test item from my site and this purchase was actually a live transaction so there is no Sandbox mode in play here. I added the item to my cart, completed the customer detail information, selected payment method and shipping method and then went to the next screen. The order page showed the item price, the correct shipping (as obtained through the USPS plugin and my webtools account data), and the correct sales tax as obtained from TaxCloud. The first problem here is that the sales tax was for the item plus shipping but shipping is not taxable in my State so that has to somehow be able to be changed; the second issue came up once I submitted the order for payment and to be transferred to PayPal for the processing. There was a discrepancy on the amount of sales tax when transferred to PayPal because a different amount was noted on the PayPal side of the process and it was less which created the "invalid invoice amount, not accepted" error notification that is sent via email. This email was sent immediately because I got the email pop-up announcement before I could even give the issue a better look.
Here is exactly how my sale breaks down: The test item was for $1.00, the USPS shipping on this item would be $5.60, for the total order amount of $6.60. The sales tax for this item (the test address was an address within my State to ensure proper testing of the plugin) calculated out to be $0.47 or 7.1% of the total order. This amount is correct but it taxed the shipping which is not taxable so the actual sales tax should be $0.07 for the item only. The total order, as calculated, now becomes $7.07 to be submitted to PayPal. Now we send the order to PayPal for payment and all of the sudden the order amount for payment is listed for a total of $7.00 which is now less than what was actually calculated and the difference is in the sales tax (it is $0.07 less now). Being as I received the email that the amount for payment was invalid indicates that PayPal received the correct amount initially but there was something that occurred during the process that recalculated something and ended up only allowing the payment of the lesser amount because that was all I could pay was the lesser amount.
I checked my entire PayPal account setup (the actual account) and there is not now, nor has there ever been, any data entered regarding sales tax, payment, shipping or anything else because I have always used an e-commerce platform and their internal modules and plugins. My PayPal plugin configuration was accurate and I even checked my shipping plugin which was accurate. I have not been able to locate anywhere within the HikaShop component where I can select an option that shipping is not taxed (and I have gone through everything to make sure) and why the sudden reduction of sales tax that creates the difference is beyond me.
Any ideas what may have happened? I have checked everything multiple times and from different angles and have found myself at a loss. Don't know what to look at anymore but would love to be able to see this work because I like the work that you have been doing and I am sure that all of the future work will be just as valuable but frustration gets the best of all of us and it has got me right now.
Thanks again for what you have done so far and hopefully there is a fix here somewhere. I will continue to look and, if I find something, will let you know what I came up with.