301 Error

do a clean cc install carefully following each applicable step:

uninstall every cc app including preferences per https://helpx.adobe.com/creative-cloud/help/uninstall-remove-app.html

then uninstall the cc desktop app, again using the correct uninstaller per https://helpx.adobe.com/creative-cloud/help/uninstall-creative-cloud-desktop-app.html#sa_src=web-messaging

clean your computer of cc files per http://www.adobe.com/support/contact/cscleanertool.html

check for, and if available, update your os

if windows is your os, repair all ms visual c++ versions that can be repaired (use google if you don't know how to do this)

if windows is your os update your ms visual c++, if it can be updated (use google if you don't know how to do this)

restart your computer (don't skip this)

reinstall the cc desktop app using the "alternative download links" at the bottom of the page at https://helpx.adobe.com/download-install/kb/creative-cloud-desktop-app-download.html

use the desktop app to install your cc programs/trials>

if that fails, you probably have a corrupt user account. google your os and how to create a new one.