I got a project and when I try import MP3, it doesn't let me? it says "after effects error, can't import file ..... unsupported file type / extension.
I've done this before but its only just a problem
Convert the mp3 to a wav and try to import that.
Using ANY kind of compressed audio in AE is always a very bad idea. Just don't do it. Convert to wav or aiff first.
Retrieving data ...