Re: Can't upload files to office 365 from Office 2010

Hi Jack,

In regard to the issue, to solve it, please try the steps below:

1. Open the upload center,  click the “Resolve” button, then click “Discard” to cancel the upload process.
2. Click “Settings” in the upload center, click the “Delete cached files” button to clear the caches in Office 2010.
3. Then  try to upload the file to SharePoint Online again.
4. If still doesn't work, please try to disable the antivirus and firewall to see if the file can be uploaded.
5. Please also check if the size of the file has exceeded the limit of SharePoint Online.

For more details, please refer to: SharePoint Online: software boundaries and limits.