I’ve just had the same experience; the block was removed after a little while. I submitted the report, and I think the subsequent screen explained that Zazzle were trialing some new security measures.
After receiving the same error, I tried logging in on a new incognito tab to bypass cookies. Once that succeeded, I switched back to the regular browser window and, miraculously, I was logged in there as well.
They are fighting the recent wave of bots I guess, which is great, but I hope they solve this issue because it’s affecting us, I can’t create new products without getting blocked then closing and reopening my browser..
I, too, just received this message today. Sent the requested error report. Hope to hear from Zazzle soon!
It is resolved now. Zazzle responded in the tech forums