FM15 preventing PW change on converted files

I'm slowly converting my databases from FMP11  to FM 15 and I've discovered an oddity.  I've converted the original FMP6 files into FMP 11.  After some pointed questions on forums about why using legacy versions of FM at all I restarted with FMP 15.  After converting the FM 11 files into FM 15 the new files will not allow me to access and make changes to the security settings to add user accounts and new passwords.  The files opened normally with their original passwords and with an empty user account ( a hold over from the original FMP 6 format which I didn't need to change initially for this conversion process ).  They allow me full access for changing fields and layouts, pretty much everything I would expect for full access to files I had created, all except being able to make changes in the security section.  I can access and make changes on any entirely new files created in FM 15, it's only the converted files that are presenting a problem.  

 What am I missing here?