If you've added files to your Box Sync folder, but your coworker cannot see them in the Box web site, there are few steps to take to resolve the issue:
First, verify that your Box Sync folder looks healthy (see this article for details):
The Box Sync folder appears in the favorites section.
Files and folders with blue check mark icons indicate successful syncing.
The Box icon appears in the system tray/menu bar to indicate that Box Sync is running and you are logged in.
If any of those statements are not true, it means there is a problem syncing your files to Box, which explains why your coworker cannot see them. Refer to the steps in the Box Sync Troubleshooting Basics guide to fix the syncing issue first.
Next, check each of the following:
Do your changes in Box Sync on your computer show up in the Box web site folder? If not, make sure Box Sync is running and you are logged in to Box.
Do changes on the Box web app appear in your Box Sync folder? If not, make sure the parent folder in Box is marked for Sync.
If you are able to see changes in your Box Sync folder and on the Box web app, the next step is for your coworker to check their Box Sync setup following the same process.
Your coworker will also need to mark the folder for Sync on their account in order for changes to appear in their Box Sync folder.
Box folders can have Sync enabled for all items, or some items. To see this, hover your mouse over the checked Sync icon on the Box web app.
If Sync is enabled for all items, any new items will be marked for Sync by default.
However, if Box Sync is enabled for some items, any new items will not be marked for Sync by default.