License Revoked (after 4 years of use)?

I purchased Acrobat Pro XI in December of 2013. It activated upon installation, no problem. Since then I've received multiple upgrade notifications, and never an issue wit upgrades. About a month ago, a pop-up appeared saying I was starting my 90-day trial. Attempting to (re) activate the software, I'm receiving the dreaded "serial number revoked" message. I've now been waiting in support chat for over 2 hours, while on hold on the phone for over an hour. I've seen all the comments about pirated software, but I bought from a reputable reseller, and how can 4 years of use and updates suddenly become pirated software? And is never picking up on chat or phone standard procedure for Adobe? This "customer support" is absolutely horrible. Adobe, please get in touch with me, or I'll be asking for contact info for your legal team.