The first step is to connect to VPN: Using GlobalProtect VPN
Next, open Microsoft Outlook and click on the File tab at the top. Under Info on the left, click on Account Settings and open the settings for the affected account.
When the Account Settings open, select to highlight the email account which is not syncing and then click on the Repair button.
The Repair Account box will open. Check your settings and fields and then click Next.
Outlook will start the process to repair the Outlook account.
It will enable network connection, search for the email account settings and log on to the server to confirm that all is fine.
Once the process is completed click Next.
Outlook will test the account settings and give you a message if all is well.
Click Close, and you will see this box. Click on Finish.
Restart your Outlook and see if this has helped you. If need be, sync manually by clicking on the Send/Receive button to initiate syncing.