I would suggest you to check and make sure Lightroom is updated to the most recent version 2015.7, click Help>About Lightroom CC.
If it is not 2015.7, click Help>updates.
Also go to the preferences tab>performance> and uncheck "use graphics processor".
Once done, restart Lightroom and let me know if it helps.
My version is 2015.6.1
I will try updating the version tonight at home.
I could not find a preferences tab.
Sent from my iPhone
The preferences are in the Edit menu on Windows and the Lightroom menu on a Mac.
But since yout trial has expired, I'm not sure if you can open Lightroom - at least I'm pretty sure that the Develop module will be disabled.
Thanks everyone. I updated to 2015.7 and unchecked the Graphics Processor (thank you Pat for telling me where to find it, as I am a Windows user). The develop tab now opens and tell me I need to pay for a subscription. I am glad it is now working but also sad that I didn't get to try it during the trial period.