Dear DK,
Good day!! Thanks for posting your concern in this Microsoft Community.
As per the description shared, we understand your concern and would like to confirm whether you have enabled any proxy or VPN or firewall on your Windows device. If yes, can you please try to turn it off temporarily and see whether you are able to sync the OneDrive on your File Explorer?
If still the same, then please suggest you reset the OneDrive sync client and check the outcome. Reference: Reset OneDrive - Microsoft Support
If it didn’t work, then can you please check whether other users in your organization are having the same issue?
Thanks for your patience and understanding. Have a good day!!
Sincerely,
Mia | Microsoft Moderator
I have encountered this same issue with a client, and have established that the end user is able to sign into Onedrive when the VPN is disconnected. Once they are signed in, they can re-connect to the VPN and everything functions normally so long as the sign in occurs when the VPN is not connected. Is there a fix for this? Or is what I mentioned the only workaround at the moment?