With their old MWS API (XML based, which is now going end of life) I managed to get the signing/encoding working (albeit, it took me a while as there is scant information for using VBA for making API calls), with this new SP-API (I think the SP stands for selling partner...its REST/JSON type), the encoding process is on another level!
Connect to the SP-API.
developer-docs.amazon.com
...it's because a URI has to be constructed in a very rigid (obtuse!) Way.... then signed, If you don't construct the URI correctly then then sign it, Amazon servers will reject. If you manage to construct the URI correctly but don't do the signing correctly then Amazon servers will reject(!), but it's not clear when you fail why you are failing (was it the URI at fault...or the signing?) Frustrating Brainache!
(
@theDBguy ..alas, that line is not the solution). Amazon provide plenty of examples for their new SP-API in python and even VB.net but as is the usual case, you're on your own with VBA! (I've never coded in VB.net and thought - with it being similar - I could pick the bones out of their examples and apply it to VBA but I failed!
(Some VB.net examples for the new Amazon SP-API....
https://www.example-code.com/vbnet/sp_api.asp )
I must have spent at least six weeks of evenings trying to get the signing/encoding to work....but nope, no workee.
So, I must relent and accept....it's beyond my abilities...so would gladly now pay someone to save me a lot more brainache now that I'm forced to go the way of their new SP-API.