Go to [OS Drive]/Library/QuickTime.
Learn to troubleshoot After Effects errors related to QuickTime.
Before you begin, make sure you have QuickTime installed. You can download the latest version of QuickTime from the Apple website.
The QT32 Server process that After Effects uses to communicate with QuickTime can crash because of a bad interaction with the QuickTime video-out system when the Apple DVCPROHDVideoOut QuickTime component is installed.
To work around this problem, do the following:
Go to [OS Drive]/Library/QuickTime.
Make a backup copy of DVCPROHDVideoOutput.component by dragging it to the desktop.
Delete the DVCPROHDVideoOutput.component by dragging it from the Library/QuickTime folder to the Trash. Enter your password when prompted.
Empty the Trash.
One possible cause of After Effects reporting that QuickTime is not installed is a blockage in the communication between After Effects and the Adobe QT32 Server, which is a component that After Effects uses to communicate with QuickTime. (This is necessary because there is not yet a 64-bit version of QuickTime.) After Effects uses TCP to communicate with QuickTime, but some aggressive firewall software and other security software can block the TCP communication.
Some non-security software—such as FileMaker and AirServer (as well as some malware, as mentioned in this forum thread)—block this communication by taking up the port that is needed. If possible, do not run software other than what's required while you're using professional post-production software.
Sometimes QuickTime fails to initialize fully because it gets stuck loading a badly written importer component. If you have any AVI importers/codecs on your Mac, they could cause After Effects to fail to recognize QuickTime.
You can test by removing the importer components (codecs) from your QuickTime folder and see if the problem persists. This forum thread provides some additional detail.
If you use AJA or BlackMagic hardware, make sure you have the most recent versions of drivers and QuickTime components (AJA for Creative Cloud, BlackMagic). Old versions of these components can cause problems with import and export of QuickTime assets, as well as problems with RAM preview and other functionality in After Effects.
Another cause of After Effects and QuickTime failing to communicate is an issue with permissions for files in the After Effects preferences directory. To force After Effects to rebuild the preferences directory and set permissions correctly (as well as reset any corrupt preferences), quit After Effects, remove the following folder, and then restart After Effects:
The issue might also be with permissions for a folder outside the After Effects permissions folder. This seems to especially be the case on macOS. To ensure that all Adobe applications can write to their preferences files, set the entire Adobe preferences folder and its contents to be read/write, not just read-only:
In some cases, QT32 Server crashes when conflicting audio drivers are installed and the Audio Hardware preferences in After Effects are set to use one of those devices.
To see if this is the problem, set your default device in Preferences > Audio to the system default or built-in outputs and see if your problem with QuickTime files continues.
If this fixes the problem, then you should troubleshoot your audio devices:
QuickTime may fail on computers with a large number of processors (CPUs), including computers with a large number of virtual processors created through hyperthreading. This is especially a problem with Apple's H.264 exporter component within QuickTime.
To get around this problem, disable hyperthreading or reduce the number of processor cores available to QuickTime.