4) Proxy settings.
Always remember about proxy settings, especially if you are working for a big corporation;
Large infrastructures frequently relay on proxy servers for several reasons mainly related to security and traffic balance.
Open Internet Explorer, Tools >> Internet Options >> Connections >> Lan Settings >> verify PAC configuration:
If everything is OK, (Compliant to organization policies) you can exclude the PAC configuration as root- cause and proceed further with troubleshooting.
5) Disable/Reenable the wireless network adapter
In many cases VPN to Office 365 connectivity issues are caused by the Wireless Network Adapter being ENABLED.
If your pc is connected to the corporate network via LAN cable, make sure the Wireless Network Adapter is OFF.
Control Pannell >> Network and Internet >> Network Connections
Right click on the Wireless Network Connection and select Disable.
6) Keep Office Updated
In several cases, has been observed how VPN to Office 365 connectivity problems have been resolved by Updating Office.
The below office updating process might be a bit more complex within a corporate environment (but not necessarily difficult). For a private O365 user instead is much straightforward:
Open any Office application, word, for example.
Go to File >> Click to: Account
Update Options > Update Now.
7) DNS Configuration:(get in touch with your internet provider or Network Team)
DNS Proximity: In most cases, when using Office 365 applications while connected in VPN and from across the corporate network infrastructure (At home, in hotel, anywhere else) the DNS servers used will be the most Proximus to the organization’s location.
Proximity becomes critical. The Office 365 servers will typically assign to the end user the closest available server. However, if connectivity to O365 seems to be constantly poor or lost, we would verify our DNS configuration with either your Internet Service provider or your Network experts.
The process below illustrates how to access to the DNS configuration for your Office 365 tenant. The feature we’ll only be accessible to the ADMIN users.
Administrators are those users who can edit the account's organizational attributes. They can Create, Read, Update, Delete or edit the Office 365 settings.
A regular (NON Admin) user wouldn’t see the admin portal after accessing to his Office 365 online on https://login.microsoftonline.com
Access to https://login.microsoftonline.com using an Admin account
Click on Admin.
Go to > Domain.
From Domains you go to DNS Settings.
Here you have the overview of the DNS setup for your infrastructure.
Verify your DNS Settings with your Network Team.
These are just some of the Office 365 VPN connection troubleshooting that I find useful. Do you have any other to add? Let me know in the comments below.