When attempting to share a file from desktop Microsoft Office via "Share" menu in the ribbon, you may see the following error:
"You don't have permission to create a new file under the current location" typically occurs when you try to write a file to a location that you don't have the write permission to. For example, when you try to share a file that you have not yet uploaded to Box, the Office client will attempt to create a file at the root level of your Box account. This will be blocked if your admin has "Restrict content creation" at root level enabled.
If "Restrict content creation" at root level is enabled, then you need to save the file in other locations than the root level in your Box account before you can use "Share" button in the ribbon.