Suddenly not able to open a lot of my documents due to "needing a newer version of pages"..?

Question

I just got my Macbook Air in early december (my old macbook was getting too old), and the ONLY version of pages I have is the newest one.
Originally, it worked fine -(it was annoying and not as good as the old pages, in my opinion however) - and I had no issues for about a month. I was able to successfully open and edit all saved files. I submitted most of them to colleagues and teachers through Google Drive, although I'd always save two copies of every document I used - one for my files and one for drive storage. Suddenly, neither will open.
Just recently, my teacher informed me that he was unable to open my documents anymore. I was puzzled by this and attempted to open the document both in drive and on my computer, but was confused when it informed me I "needed a newer version of pages". I have the NEWEST version of pages. This document was saved on the NEWEST VERSION of pages.
About half of my files - both on google drive and in my storage - are now unable to open or even convert due to me getting a notification saying "I need a newer version of pages".
A lot of the files I received were downloaded through google drive as Microsoft Word files, and were automatically converted. They worked fine as a pages document when I received them, and was able to successfully work on them and complete them and then resubmit them through Google Drive. A month later, these same files will not open, due to me needing a newer version, but no newer versions are even available.
My mac also has a remote disc - everything from my old laptop was transferred to my new by apple when I bought it.
However, the old files are not the issue. It's the files that I've downloaded and editing since I bought my new laptop that are the issue.
I'm also not a genius with computers - I've used a mac since 2011, but have never really encountered issues that needed me to really "get to know" the innerly functions of the computer until now.
Help? Some of the said documents are very important to my work and I need to be able to succesfully submit them so others can open them through google drive or dropbox.

Answer 1

I've seen other people solve their issue this very same way, based on other conversations, but my case is different. No older version of pages exists on my laptop.
My laptop is new, so I have no older version of pages anywhere on my laptop - I never installed it.
All files that I transferred from my old laptop to my new laptop that were made using the old pages still work, but a majority of the new documents that I've created since getting my new laptop will not work.
After further investigation, the ONLY files that will not open are files that had been converted from Microsoft Word to pages and then saved.
So, on my new laptop, I would download a file from another user through Google Drive and then convert it from Word to Pages.
The pages documents worked, and I saved them successfully, and I could reopen them when I first created them.
But now, checking them again a month later, all files and only files that had been converted from word to pages say that "I need to update to a newer version of pages" - but all files that were created in pages by me work fine. And so do documents that I downloaded AS pages documents.
This is the notification I see whenever I try to open a file that was originally a word document. All ex-word format pages documents that I converted from word to pages give me this notification and will not allow me to open the document. They worked originally, but now suddenly do not.. why?