I downloaded InDesign on a second computer and version 2017 was downloaded. I had been using 2016 on my first computer so all my files had been created using 2016. I opened each file and saved it as a 2017 file. However, one file opened showing it was already converted (which it was not) and all that was displayed on the screen was a grid pattern. I even restored the back-up version just to be sure the file didn't somehow get converted but it was the same problem with the restored file.
Any help would be appreciated.
I saved the file again and it resolved the problem.