I am having the same issue as you Philip M.21. Have been communicating with Dropbox support for a week trying to resolve it with no luck. Install 30.4.22 works fine but once it autoupdates to 31.4.25, the app stops working and disappears from the system tray etc. You can successsfully reinstall 30.4.22 to allow sync momentarily until autoupdate kicks in. I am running Windows 10 Enterprise withh Windows Defender on a domain user account. This issue with version 31.4.25 does not occur on a pesonal Windows 10 computer with Windows Defender, or a personal Mac running Sierra.
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