Hello John,

Finale 2014 and newer use a different file format (.musx) than previous versions 2012 and earlier(.mus). So, unfortunately, this file type can't be opened in Finale 2011. If you have access to the newer version that created this file you can export the file (File > Export) as a MusicXML file or a Finale 2012 file both of which can then be used in this version.

I give a brief tutorial in this thread. There are things you need to know about the process as 2011 has a few differences:

https://makemusic.zendesk.com/hc/en-us/community/posts/115000949067-saving-a-2017-document-to-an-earlier-version?page=1#community_comment_115000966067