Indesign Book wont synchronise master pages to parent pages

I have an indesign book created approximately 2 years ago to manage consistent formatting of a series of documents. 

I notice that Indesign have more recnetly changed from the term 'Master Pages' to 'Parent Pages' and ever since this change my book wont sychrinise. 

Files created prior to this change still have master pages, even when I do a save as. Files created after this change have parent pages and will only sync with other files that have parent pages, but not master pages.

Please let me know how I can update my old files to have parent pages, or how to make my book sychronize with either master or parent pages?