Hi there, Charlotte.
This error message occurs if you're not loged in as the administrator when opening an older file into a newer QuickBooks version. You'll need to log in as the administrator, the convert your company files into the new software version.
You can check out this article on how to upgrade or convert a company file: https://quickbooks.intuit.com/community/Getting-Started/Upgrade-or-convert-your-company-file-to-a-ne...
If you don't have an administrator set up, just follow this article to create a new one: https://community.intuit.com/articles/1762718
If you have more questions about QuickBooks, just leave a comment below. Thanks!