The first time the user logs in after the upgrade, they will need to be connected to the internet. This is because the log in credentials need to be updated for the iOS 8 changes.
After that first time, the user can then work offline. However, they will need to Open the Tools menu (icon with 3 horizontal lines in the upper right hand corner). They should then select Settings and tap on Server Connection to turn it off. They will then be able to log in using the offline mode.
We understand that this is a change from the previous version that automatically detected the internet connection upon log in. We have submitted a ticket with our development team to get this fixed. In the meantime, the above will get the user into naturalForms when there is no connection.