I purchased my CS6 key from adobe... this week it decided the # is invalid

What is the exact error message or code you're seeing? 

Have you run the Adobe cleaner tool and reinstalled CS6.  A corrupted hosts file could be preventing activation.  Doing a clean reinstall might help.

https://helpx.adobe.com/creative-cloud/kb/cc-cleaner-tool-installation-problems.html

serial numbers can be black-listed for several reasons.  one is when an initially valid serial number is found to be publicly available. ie, your number's provenance is no guarantee it is valid.

you can try contacting adobe support to see if they'll check.

use a browser that allows popups and cookies and contact adobe support by clicking here, https://helpx.adobe.com/contact.html?rghtup=autoOpen
in the chat field (lower right), type AGENT
be patient, it can take quite a while to reach a human

p.s you can also use phone (but chat is usually quicker), https://helpx.adobe.com/contact/phone.html

p.p.s. you can also use twitter to tweet @AdobeCare

p.p.p.s. if you're contacted by anyone (via email or private message), it's much more likely to be a scammer than an adobe representative. ie, double check for an employee badge if contacted in the forums and look for an adobe.com domain in the email address if you click reply to an email. then check again and be very suspicious. any other method of contacting (or offering to contact you) is almost certainly a scam, https://community.adobe.com/t5/using-the-community-discussions/staying-safe-in-the-adobe-support-community/td-p/12919684/redirect_from_archived_page/true

Moved to Account, Payment, & Plan forum, from the Photoshop forum.

Hi @Mark_inNJ 

We cannot assist with this issue on this forum. You will need to contact Adobe Customer Care directly. Do not respond to PMs, as they are likely to be scammers.

Try the link to auto-open the Chat:
https://helpx.adobe.com/contact.html?rghtup=autoOpen 

If your browser blocks the Chat window, try the troubleshooting tips here:
https://community.adobe.com/t5/creative-cloud-services/how-to-contact-adobe-support/td-p/11875703 

If you can't find out why your browser is blocking Chat, you can also send a tweet to @AdobeCare.

You can find phone numbers here (you may be on hold for a while):
https://helpx.adobe.com/contact/phone.html 

Please report back.

~ Jane
Forum volunteer