I received a CS5 file and got an error message when opening saying several plug-ins were missing. I read that this particular error can occur when you're trying to open a file from a different version, but the file info says it's CS5. I've got the latest patches for indesign and extension manager, but when I look in extension manager it shows the plug ins with a lock beside it. How do I unlock those? Thanks!
It’s not likely to be a CS5 file. Your system knows nothing about later versions.
You’ll need to get whomever sent you that file to save it back via IDMLO.