If you received the file from someone else, ask them to save it as a "Compatibility" project. Go to File > Save As > Save a Copy as [Previous Version]. Step 2: Identify Missing Plugins
If you don't need the effect, delete the missing effect layer and resave the project. Step 3: Purge Memory and Disk Cache
This error typically stems from a version mismatch or a missing dependency. When After Effects opens a file, it builds a database of properties. If it finds a property tag that isn't defined in its current library, the system stalls. Common triggers include: