Not having a Mac I'm not completely sure, but your solution will probably go along these lines.
Deactivate your serial-numbered license.
Then try to run Photoshop, and log in with your cloud-enabled Adobe ID when prompted.
Note that activation of your cloud subscription may take a little time (hours to possibly days) after you've paid.
Noel, thanks for your helpful reply.
Jeff tranberry intimated that the error code i got was probably due to some absent component in my PSCS6 (perm lic) install.
I deactivated PSCS6 and then uninstalled PSCS6. I then went to CC and downloaded the CC version of PSCS6. This went smoothly. Subsequently I ran update from HELP menu and a number of apps were quickly updated.
There was no "TRIAL VERSION" problem.
In addition, my cloud subscription was activated in minutes.
thanks to you and jeff tranberry.