I Can't create a new file in Illustrator CC

REset your illustrator preferences

https://community.adobe.com/t5/illustrator-discussions/how-to-reset-illustrator-preferences/m-p/10602277

Some trouble-shooting steps:
• Try re-booting the computer.
• Check physical connections of any devices attached to the computer.
• Check for updates to Illustrator and your computer's OS.
• Check for updates to video card drivers.
• Check for updates to other hardware and periphreals.