If the error occurs immediately upon loading an older template file, it is highly likely an issue with the layout architecture. File > Scripts > Update Legacy Expressions.jsx
Open the newly imported composition folder. This action strips out broken environmental settings and frequently bypasses the "unknown property" block. 4. Reinstall Plugins and Re-register Pseudo-Effects
How to Fix the "After Effects Error: Asked to Create Unknown Property of Type"
If you are opening an old project (e.g., from 2020-2023), AE might be struggling with deprecated expression syntax. Go to the menu. Navigate to Dependencies . Select Update Legacy Expressions.jsx . Run this script and save a new version of your project. 2. Import into a New Project (If You Can’t Open It) If the error occurs immediately upon loading an
To avoid and troubleshoot this error, follow these steps:
Many advanced presets utilize custom control panels (pseudo-effects). If the matching XML definition or plug-in (like Magic Bullet Looks or Boris FX Continuum) is absent or outdated, After Effects panics.
: C:\Program Files\Adobe\Adobe After Effects (version)\Support Files\Scripts\ScriptUI Panels Navigate to Dependencies
When you download a project template and are missing the plugins (like Red Giant, Video Copilot, etc.) that the project relies on, expressions will break and cause this error.
1. The Clean Project Import Method (Best for Unopenable Files)
In some cases, switching the engine back to the older version helps. Go to File > Project Settings > Expressions and change the engine to Legacy ExtendScript Restart Extensions: If you are using extensions like Mt. Mograph Motion Backup the original first.
If you are writing custom tools and encountering this error (e.g., asked to create unknown property of type "ADBE Vector Graphic" ), your script is requesting an invalid internal property string.
This violates Adobe’s support terms, but it has saved many projects. Backup the original first.