Reinstall the program and/ or fix your system's user privileges and file permissions plus turn off security tools that may block access. The files in fact are most likely all there, but since you haven't used it like forever, they probably have been marked in some way...
Thank you very much for your answer. I reinstalled the program and checked my system's user privileges, but it didn't fix my problem. However, I realized that many effects were duplicated at several locations on my hard drive. So I deleted all superfluous copies, and now everything is working. :-)
But, unfortunately, another problem has occured... Indeed, when I ask AE to open my most complicated composition, I got a series of error windows, and then After Effects crashes.
Now, what puzzles me is that in every other compositions, the plug-ins "Photocopy" and "Spill Killer" are working perfectly well...
Do you know what I can do about it ? :-//
Thank you for your attention :-)
What happens if you try to import that project into a brand new project?
Thank you for your answer.
I can import that project in a new AE project. But then if I open the problematic composition, I get the same error messages. And then AE crashes...