suddenly, a little over a week ago, I became limited to one octave.  I thought it would just come back but it hasn't.  I never heard of this.  Anyone have any helpful thoughts?

Hi Jack, did anything happen that may have affected your voice, like overuse, a cough, allergies, etc? 

If you're experiencing hoarseness or loss of range for 2 weeks or longer, call your doctor! See below for more info on vocal health & injury:

https://www.30daysinger.com/blog/vocal-nodules-preventing-injuries