I have the newest Pages 4.3 and Yosemite 10.10 so the report makes no sense, Pages has been messed up. I tested the conversion between pages file and zip and it recompiled pages to a folder but it did not work — only getting the error: you need the new Pages.
How can I fix this I-Cannot-Open-Any-Pages-File-On-My-Computer-Anymore with Pages?
Best Answer
You need to go to the Mac App Store and install the latest version of Pages (5.x)
As of now, the latest version of Pages is 5.5.1, and it's only available from the App Store.
I've seen this when using Pages from iWork '09, which is 4.3. The file format changed and iWork '09 cannot directly open the new files.
You can export iWork '09 compatible files from Pages 5.x though.