After Effects error: file '____.mp4' cannot be imported - this 'Moov' file is damaged or unsupported

[bluepyramidjay]

Hi, 

I am a freelancer, self taught graphic designer. I recently purchased an Instagram stories pack that uses the ATOM extension in After Effects. When trying to import a template I get all kinds of errors including the subject headline. I also get After Effects warning: effect control conversion required in effect "Keylight (1.2)". Some effect controls will be reset. To avoid silently resetting these same effect controls on all subsequently loaded projects, save this project and then quit & re-launch After Effects. (25 :: 0).

[Dave Merchant]

Sounds like whatever you purchased was designed for an old version of After Effects, before many of the Quicktime codecs were dropped. The Keylight warning can probably be ignored unless it's obvious that something isn't looking right, but if you have source files that use legacy QT codecs there's nothing you can do about it; they will have to be converted before After Effects (or anything in CC) will read them.

See https://helpx.adobe.com/x-productkb/multi/quicktime7-support-dropped.html