Please check Cinema 4D installation when After Effects installation
From 2020CC, C4D lite is separately installed. When AE is installed or update, C4D is installed replaced currently installed version. This behavior is very bad for commercial Cinema 4D users. In AE installation process, please check Current version of C4D and if R21 is installed, please don't installed Cinema 4D. It should install C4D lite, when R21 is not installed.
Julian Bleecker commented
I had this same issue happen to me. I wonder if I try to install AE 2020CC again it will cause the same issue. I spent a day or two trying to figure out what had happened, and then reinstalling including all my configurations and plug-ins. Really bad.
Dan Hildebrand commented
I'm surprised I couldn't find more info on this, but yeah. Just happened to me where I tried to update AE and it actually replaced my installation of C4D R21.115 with an earlier version.