Why did my purchased version of Cp8 suddenly turn itself into a trial version?

Why did my purchased version of Cp8 suddenly turn itself into a trial version? I'm trying to locate the serial number that came with it, hopefully it will reinstate.

I'm used to this software doing some weird stuff, but turning itself into a trial version?

I bought the software, did not upgrade from a trial version. I'm using Mac, Yosemite 10.10.5, 24gig RAM, ATI Radeon HD 5770 1024 MB.