FabFilter

I have a recurring problem with Timeless. several times now, I have saved a session with the Timeless plug-in inserted on a track, and at some point later reload the session and the plug-in is deactivated (greyed out). When I try to reactivate the plug-in I get the message "The plug-in could not be made active because the plug-in is not present in the plug-ins folder." But the plug-in is in the folder, and Pro Tools will let me start a new instance of it on any track, but there's no way to reactivate the original version with my edited settings (I didn't save a settings file backup, although I will in the future). I have had this problem occur in 5-6 different sessions so far.