AE can only load as a render engine, main screen is all greyed out

adobe has a help page on this. there may be a text file in your documents folder you need to delete to stop it automatically launching the render version. Check on the adobe page, their solution worked for me when i had the same issue.

This might be a dumb question but are you trying to open AE from the Programs folder?

Start by checking your user account in the CC app and on the web site. In case of doubt, sign out and deactivate, then sign in again. Usually this odd behavior simply boils down to that - AE thinks it's unlicensed for whatever reason.

Mylenium