Your Offline Passcode is only valid until you use the Log Out button, in the OnBoard iPad app. This means that you'll be asked to create a new one after logging in, whenever you've just previously selected to log out manually.
If you happen to see the "Enter Offline Passcode" screen, but you cannot remember the offline password that you've chosen, it can be reset, but you must first re-connect to the internet. Here are some steps to follow, if you cannot remember your password.
If you do not remember what this password is,
1) Reconnect to the internet. This can be done by pulling the hidden dock up from the bottom of the screen and using the WIFI button to reconnect to your nearest access point:
2) After reconnecting to the internet, and returning to OnBoard, you will still be prompted to confirm your offline passcode. From here, we just need to "Force Close" the application, and launch it again. To do this, double tap the iPad's Home button, just below the screen. This will bring up a list of apps that are currently running on your device. Find OnBoard in the list, and use your finger to slide the app up off the screen like this:
3) Now, just re-launch the application from your iPads desktop, and you should have access to your meetings as normal, since you are online.
4) If you would like to reset this offline passcode, click the icon in the top left of the page that looks like three horizontal lines. This will open a side panel. Click the LOGOUT button at the bottom of this page.
Upon logging into OnBoard the next time, you will be asked to create a brand new Offline Passcode, and verify it.