Just so I can understand the situation fully, can you clarify what you referring to exactly? Are you running a proxy server on your machine perhaps?
If you check the desktop app preferences, can you send me a screenshot of the settings within the Network tab. You can access this by clicking the Dropbox icon in your menu bar/system tray, clicking the profile pic/initials icon in the top right and choosing "Preferences...".
Let me know and we'll take it from there - thanks!