please make an internet connection and log in. sometimes you need to connect to internet so Adobe can verify you are a paying membership.
Hope this helps.
If issue is with the Photoshop CC 2014 on a Windows computer, it may be an issue with graphic card driver.
Navigate to C:\Program Files\Adobe\Adobe Photoshop CC 2014 and rename sniffer file to Sniffer _old.
In case, Photoshop works fine after renaming sniffer, contact graphic card manufacturer and update graphic card driver.