If the project uses a plugin you don't have installed, After Effects might struggle to define the properties associated with that plugin. How to Fix

Click "Yes" when asked if you want to delete the preferences file. Step 5: The "New Project" Import Trick

⚠️ Always keep "Auto-Save" turned on in your Preferences to ensure you have earlier versions of your work to fall back on if a file becomes permanently corrupted.

Opening a project created in a newer version of After Effects. Missing plugins that were used in the original project. Corrupt preference files or cache data. Expression errors that reference non-existent effects. Step 1: Check for Version Compatibility

How to Fix the After Effects Error: "Asked to Create Unknown Property of Type"

If the project file itself is slightly corrupted, you can often bypass the error by importing it into a fresh workspace rather than opening it directly. Open After Effects and create a brand new project. Go to File > Import > File. Select the problematic .aep file.