Hi Szalam, the codec solutions that provides is outdated, sadly none of it applies to the latest versions of Mac OS. There is no longer a Quicktime codec folder in the Library.
Oh, right, darn.
What happens if you create a QuickTime file using the PNG codec yourself?
Does Premiere Pro import the file you're trying to work with?
What about Adobe Media Encoder?
I too am having this problem, but it's when I import an .mp4 exported from Media Encoder using Best Settings .h264.
I re-rendered the file a few times and eventually it imported okay so I was able to work with it. Suddenly, a few weeks after importing it , AE is giving me this error again and not loading the .mp4.
Any advice? I will have to try rendering to different formats as a temporary solution but .h264 should work.
I have some very serious advice, DO NOT create an H.264 to then work on it in After Effects. H.264 is a highly compressed format! You only want to use it at the very last step of creating a deliverable. You do NOT want to use it in production! Instead create a file with a technically lossless or visually lossless production codec. Something like Cineform, DNxHR, or the like.