Hi @Rachel
Did you share the files via OneDrive?
If so, do you and staffs all use OneDrive for Business, and use accounts with the same organization's domain name?
If staffs open the shared files via browser, it's recommended to clear browser cache and cookies, open a "New InPrivate window" in browser, copy the shared files link to it.
I also suggest staffs change the browser for a test.
Any updates or misunderstanding, welcome to post back.
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