Thank you for your assistance.  

The main login did accept my full 25-character email address, but told me that my password is incorrect.  I'm using Linux, so have middleclick-paste capability.  I write all the registration information in a textfile, kept on a USB stick.  I open this textfile in Geany and then highlight-and-middleclick into the registration page's individual entry fields.  Conceivably, I might have absent-mindedly pasted-in the password from another pool.  Or, equally conceivably, a cosmic ray may have flipped a few bits either in his server's memory or on its hard drive, thus blowing either my email address or my password into the netherworld.  I've been using personal computers since 1985 and have twice experienced data changes which there is no other way to account for other than by random bit-flips in RAM.