Hi ,
Welcome to our new Microsoft Q&A Platform.
Based on my understanding, your issue is that Office 365 product reported that they do not have an internet connection when using Pulse VPN. Is that right? Please feel free to let me know if my understanding is wrong.
What's the OS version of your VPN client?
Based on my research, office 365 under Windows 10 uses the Network Location Awareness (NLA) and the Network Connection Status Indicator (NCSI) to discern whether an active network connection is available. Both of these rely on there being a default gateway specified for the current active Internet connection for them to successfully report the connection is up.
Third party VPN clients with no default gateway might prevent office from working properly. So please first check if you have a blank default gateway.
Check if the following link is helpful:
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
Hope this can help you.
Best Regards,
Candy