Problem with DUO 2FA configuration

[Matt Sardi]

Good Morning, 

I am hoping that someone can provide me with some documentation regarding an issue that I've encountered (there doesn't seem to be any documentation regarding my specific problem at this time). 

I've configured and enabled DUO 2FA for all Atlassian accounts and it's been tested and proven to work for all accounts except for one. The one person can log into Atlassian and does not receive a DUO prompt.

The question that I have is: 

What if a user is showing two active sessions on two different computers -- does this effectively cancel out the DUO 2FA due to the active sessions continually refreshing? Would logging the user out of all sessions force the user to reauthenticate and receive the DUO push normally?