If you see: ...unknown property of type... in an expression. Check your code for effect("name") . Make sure that exact effect is applied to the layer. If the effect was renamed, update the name in the expression. Scenario B: Using .value or .valueAtTime
If AE opens correctly, add your scripts back one by one until the error reappears to find the "troublemaker". 2. Refresh Extensions (For Motion v4 & Similar) If you see:
Code is trying to apply a 2D position property to a 3D layer, or vice versa, causing a type mismatch. Make sure that exact effect is applied to the layer
If the error occurs upon launching After Effects, a script in your startup folder is likely the culprit. outdated expression template
The "Asked to Create Unknown Property" error is a common headache for Adobe After Effects users. It usually pops up when the software encounters data it doesn't recognize within a project file. This often happens when moving projects between different versions of After Effects or when using third party plugins. If you are stuck with this error, here is how to resolve it. Understand the Cause
The bug usually happens when Adobe After Effects tries to read a third-party script, outdated expression template, or an unsupported pseudo-effect that your current software version cannot recognize . This error can interrupt your workflow, cause random software crashes, or block you from opening a .aep project file entirely. What Causes the "Unknown Property of Type" Error?