True Type font issues

For awhile now I'm getting messages that Century Gothic TT is missing -- from files that I've used for years and packaged, and never had font issues with before. I do work on a Mac at home and PC at work and I sometimes open the docs at work, and will save, but not repackage. It seems like every doc tells me that Century Gothic TT is missing and I have to go through Find All and replace repeatedly with Century Gothic OTF. What am I missing or what's changed with InDesign's font library and how do I get out of this font fixing for every.single.document?