Cannot attach files to desktop Outlook client (Office 365 and Outlook 2013)

I've posted this issue in the Office 365 and Outlook 2013 communities and was directed to post this issue in this forum.

I have a user that cannot attach files when using their Outlook desktop client (Office 365 and Outlook 2013). When they try to drag and drop, or when they use the "attach file" button they get the following message - "You don't have the appropriate permission to perform this operation". This only happens when they use Windows Explorer. This issues still happens when Outlook is ran in Safe Mode. I tested the user's Outlook account from another computer and was able to successfully attach files, so the issue seems to be related to the user's computer. I was also successfully able to attach files by using the user's OWA. Any help with this issue would be appreciated.

Here are the steps I've already tried:

- Checked all permissions and they are correct

- Ran Windows update

- Ran Outlook at Admin

- Ran PST repair tool

- Created new profile

Thanks!