The program opens but I am unable to do anything in it. I can click on the tabs at the top but every single option is greyed out. I have restarted my computer several times. I have updated my CC software successfully and am still getting the same problem. I cannot work on any Illustrator files and I am not able to meet my deadlines. Down with creative cloud.
Other than reinstalling (see below) the only thing I can think of is to ask in that forum Illustrator
Discussions of RE-installing
-using the cleaner after uninstalling and before reinstalling will usually help