Relicensing Acrobat Pro DC, won't take key or product code

I have been using Acrobat Pro DC for months -- no problem with original setup and licensing.  Then it kicked me out.  I am trying to type my Product Code or Key into the "Serial Number" boxes to relicense, but it won't take letters.  Also, there are six boxes for input and my Product Code and Key both have five blocks.  What do I do?  More details below.

Friday I started getting a screen which said that licensing was required and gave me an option to start my 32,767 day trial or license the product. I started the trial (it was 87 years, after all -- should be good) but today it said my trial had expired.  No problem, I dug out the disk and the email, both of which have five block codes, one called the product code, one called the Key.  The product code came off the installation DVD sleeve.  The Key came off of the email with download instructions.  They are different.

After signing in, I am required to enter my serial number.  I've looked all over the CD cash and other materials for a serial number and don't see one.  I checked the website for instructions on finding a serial number and the only thing that's there is the Product Code.  When I try to enter the Product Code, it won't let me because the first field takes only numbers, while the Product Code begins with a letter.

This is very disappointing for a product which already is overpriced and much worse than prior version.

How do I fix this?