This is most commonly a cookie setting for MacOS/iOS/Safari members.
Cookies are used to determine if someone is logged in and has access to the files and if they are blocked the file won’t load.
Please make sure Safari isn’t blocking cookies from the site.
Here’s a link that will help you check the settings ( https://www.whatismybrowser.com/guides/how-to-enable-cookies/safari).On a Mac
Please try this and if it doesn’t help or if you’re experiencing this issue on a non-Safari browser, contact support.