I purchased the standalone version of Lr version 6 back in Feb 2016. I've been using it for a while and everything was fine until yesterday my PC rebooted and now it's using CC 2015 version and ask me to start a trial. I already paid $149 USD and now I have to pay again?
Open LR and go to the Help menu. Sign Out if you are signed in and then Sign back In using the same Adobe ID you used to buy it or the one you set up when you first installed LR 6. you will then be asked for the serial number so input that.
That worked :-)
Thank you for your help.