I left this thread hanging, and might as well bring it to closure.
I contacted HBI through their website. I got a rapid response that said "provide your receipt and we will give you a full refund." Unfortunately, I bought it online and couldn't find any proof of that transaction. The reply took a little longer, but it was "sorry, no refund without a receipt."
My next step was to dig out the owners manual. I found out how to turn off the automatic shutoff, which I did and now it stays on with the AC power source. I also recalibrated it per the instructions.
The final analysis is: It works pretty well now. Weighing my improvised check weights shows a couple of .01's high initially, but if left on the pan for 20 seconds or so, they gradually drop to what they have always weighed. It's become slow in its old age, kind of like me. Knowing that caveat, I think that I can still use it for what I do, which is generally to verify something. It's not my primary method to weigh charges.
Thanks again everybody for your help!