Hello Adam,
Everything seemed to be fine with the USPS Avanced shipping app. I was using the original "web tools API Username" from my working site. It was working and everything but then this e-mail arrived :-
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You are receiving this message because you have been identified as an integrator that is still utilizing a non-secure Web Tools endpoint (http://production.shippingapis.com/). Please use the Web Tools Secure Production endpoint (https://production.shippingapis.com/) to avoid any possible service disruptions
(By the way the links are odd being the same and also don't work just show a rather odd xml file).
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So I went to USPS https://developers.usps.com/ and logging in under my original info. went though the steps and ended up with a Consumer Key and a Consumer Secret key from the Credentials section. Also called client ID and a client secret, respectively. No sign or mention of a "web tools API Username" anywhere.
I replaced the "old" API username with both the Consumer key and aslo tried the Secret key neither worked. Thinking perhaps the name had been changed from the old j2store. So then I placed the old key back in there and of course it worked. So not wanting to be a "bad integrator" I wondered what I missed.
(Been called a lot of things but "bad intergrator" seems rather ominous, will that give me cred if I go to a tec show?)
James