If you are having problems saving with Box for Outlook, here are a few steps to troubleshoot the issue:
Some files may not upload, this is usually due to a naming convention that Windows does not support such as (\, /, ", :, <, >, |, *, ?).
Try disabling any firewall or anti-virus software temporarily, as these programs can cause disrupted connection to Box.com (please note that this may require you to restart your computer). If this solves the problem, you may need to configure your software to allow connection to Box.com. For firewall configuration instructions, please see: Configuring A Firewall For Box Or Box Sync
Are you using a wireless connection? Try connecting directly, as weak or intermittent wireless signal can cause conflicts with uploads.