Try to save as IDML, then open again. That's mean the file is created on a new indesign version.
It's a stupid message. It means the file was made in a later version and so that's why you cannot open it. Y'all should be working with the same version of ID. You can have them save as an IDML which should then open. However, there will likely be at least text reflow issues as each version tweaks how type works.