I'm quite familiar with this old error and how to avoid it, cleaning de cache etc... but it seems to be coming u p again and again in my AE CC 2017. Both blue and green bars are gone... so I have no idea how to fix it... i've been working on it for days, and everything was alright until a few hours ago.
Purging cache won't fix it..., reopen AE won't fix it...
I'm using AE 184.108.40.206 (2017 release!) on Mac Mini 2.8 GHz Intel Core i5 with 16 GM of RAM