Have you tried, for example, the ebay/UPS integration? It's a disaster. It's expected by their customer support that while the UPS site shows the ebay credentials that they won't work for at least an hour.

Have you interacted with UPS's technical support on anything? They're a disaster, and aside from the example I mentioned have in the past waved off other bugs as being expected.

Have you tried shipping in general using UPS's website? You need to understand a lot about their system to really use it (for a simple example, the difference between "UPS account" and "having a working login under which you've provided your EIN").