Hi Vincent. I'm Greg, awarded MVP for eleven years, Volunteer Moderator, and Independent Advisor here to help you until this is resolved.
Briefcase has been completely replaced by services like Dropbox, Microsoft OneDrive, Google Drive and Offline Files. Like the Windows Briefcase, these services synchronize copies of your files between your computers.
More here to understand all replacement options available:
https://social.technet.microsoft.com/Forums/en-...
https://www.howtogeek.com/396628/what-was-the-w...
https://www.techmesto.com/how-to-enable-briefca...
https://www.tenforums.com/tutorials/122727-enab...
https://www.windowscentral.com/how-get-started-...
https://www.tenforums.com/tutorials/116029-turn...
https://www.blog.google/products/photos/introdu...
I hope this helps. Based on what you report back I can answer any questions and may have other steps to perform. If you'll wait to rate whether my post was helpful, I will keep working with you until it's resolved.
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