Could not read from source

Hi @theo_8556,

Sorry to hear you're experiencing this issue. Based on the error and the involvement of cloud-synced files, try manually deleting the media cache files.

You can see where the media cache is stored in Edit > Preferences > Media & Disk Cache, but don't clear it from there.

1. Open the folder location shown in the prefs, which by default is C:\Users\<your username>\AppData\Roaming\Adobe\Common
2. Quit After Effects
3. Inside that Common folder, delete the Media Cache and Media Cache Files folders
4. Relaunch After Effects

When you replace or reimport the files, is the same error shown?

- John, After Effects Engineering Team 

I am using AE v24.6.1. I am on windows. The footage is MP4. The project is stored on OneDrive then documents. The footage is stored in downloads. I'm not sure about the storage media. The project file doesn't have any special characters. Finally, how do I check if After Effects has the permission it needs. Thanks. 

Sorry to hear that things are not working as expected.

It would help to know some more details.

Which version of After Effects are you using?  22.6.5, 23.6.9, 24.6?

Which operating system are you using?  macOS or Windows?

What are the source footage file types?  PSD?  AI?  PNG?  MOV?  TIFF?  GLTF?

Where is the project file stored?  Desktop?  Documents?  External USB drive?  OneDrive?

Where are the source footage files stored?  Next to the After Effects project?  Desktop?  Documents?  OneDrive?

How is the storage media formatted?  HFS?  HFS+?  Fat32?  ExFAT?  NTFS?  APFS?

Does the project file name or any of the source footage filenames use special characters?

Does After Effects have the permissions it needs access folders/directories associated with using it?