That's when things got interesting. The system told me that it had no record of my email address! Being a good academic, I checked all email correspondence I had with Amazon and verified that yes indeedy, I was using the correct email address. (It's the only one I have ever used with Amazon, but checking is always good.)
So I emailed Amazon's customer support, and got this reply (emphasis mine):
I am very sorry that you have experienced difficulty accessing your account.....You can reset your password online through the Your Account area of our Web site, or by clicking this link:
Enter your e-mail address in the space provided and click "Continue." We will then send you an e-mail containing a personalized link. Use the link, enter your new password twice (to confirm it), and click "Submit your password." Once you have taken these steps, your new password will be effective immediately.
Please note that this does not address the problem--it assumes that the system recognizes my email, when in fact it appears to be the email, and not the password, that is the problem. (Well, if the system has lost my email, then likely it has lost the password, too!) I emailed back pointing this out, and also noting that it has been less than a month since they upgraded my seller account to Tier II status (using that selfsame email that now the system does not recognize, after they initially told me I *had* no account--then a human being found it), and got the following email in return:
Did we successfully answer your question?
Below were two options, a link for yes and one for no. Obviously, I clicked NO, and restated the problem, this time with a query as to whether initial emails were actually read or whether customer service just answered the most common question rather than the one actually asked.
I am awaiting their response.
Up until now I've never had trouble with Amazon, but I have to say that in this case Amazon service is made of fail. Clearly there is some problem on their end--they couldn't find my seller account the first time I tried to upgrade, but then they did when I was persistent; now the system as a whole does not accept my email, even as a buyer. Sigh. All I want is for them to fix it, but they can't fix it until they actually *address the problem*.