This is especially common in After Effects Beta versions, where, as noted by the After Effects Engineering Team, deleting the ModifiedWorkspaces and OriginalUserWorkspaces folders in the preferences can resolve the issue.
If you encounter this issue right after installing a new utility, a bad script or plug-in is likely confusing the internal software schema.
When custom tools build shape layers or effect structures programmatically, using an outdated ADBE match name will trigger this exact error dialog. Step-by-Step Fixes for the After Effects Error 1. Update Legacy Expressions This is especially common in After Effects Beta
If you are working with a Motion Graphics template (.mogrt) from Envato or Adobe Stock:
If you're still stuck, these advanced methods can help: Step-by-Step Fixes for the After Effects Error 1
This violates Adobe’s support terms, but it has saved many projects. Backup the original first.
This error message is Adobe After Effects' way of saying that it cannot find or recognize a specific element within a project, script, or expression. It expects a particular type of data—a property, a layer, an effect, or a numeric value—but is receiving something else. The phrase "unknown property" indicates the software is being asked to create or access something that doesn't exist in its current state. This error message is Adobe After Effects' way
Now for the part you're really here for. Below is a series of troubleshooting steps, starting with the least invasive and moving to more involved solutions.
Sometimes, a simple restart can resolve the issue. Close After Effects, wait a few seconds, and then reopen it.
Run the built-in Adobe Expression Update Script to automatically convert legacy mathematical arguments into modern JavaScript engine structures. 3. Change the Expression Engine Type
Here is a deep dive into why this happens and how to fix it.