Creative Cloud Sync

first try, resetting the cc app: To reset the Creative Cloud desktop app, make sure it's in the foreground, then press:

Win: Ctrl + Alt + R
Mac: Cmd + Opt + R

if that fails, do a clean cc install:

uninstall every cc app including preferences, https://helpx.adobe.com/creative-cloud/help/uninstall-remove-app.html
then uninstall the cc desktop app, https://helpx.adobe.com/creative-cloud/help/uninstall-creative-cloud-desktop-app.html
clean your computer of cc files per http://www.adobe.com/support/contact/cscleanertool.html
restart your computer (don't skip this)
reinstall the cc desktop app, https://creative.adobe.com/products/creative-cloud.
if you're unable to install the cc desktop app at this stage, use an administrator account (solution 4 here, https://helpx.adobe.com/creative-cloud/kb/creative-cloud-missing-damaged.html)
use the desktop app to install your cc programs/trials