To follow up, after a fair amount of back and forth via the contacto web page, I finally got another link for 'reset password' from Iberia. Unfortunately, they sent it to my email when I was out, and it had only a 3-hour expiry (which is fine for an immediately requested link, but terrible for a CSR reply sent via email). The page informed me it was expired, but suggested I ask for a resend. I did and to my surprise it worked!

I don't know if customer service fixed something on the back end, or if it's just serendipity. However, I've decided that I'm going to transfer any CC earned Iberia Avios to BA regularly. BA's web site has its problems, but it's far less likely to keep me out. I think their award space is pooled anyway, after all Iberia Plus is owned by BA.

Thanks for all the suggestions.