Here’s how to close out of the posBoss app and restart. This refreshes the app and can help resolve small issues.
For new iPads that no longer have the physical button.
From the Home Screen, swipe up from the bottom of the screen and pause in the middle of the screen.
Swipe right or left to find the app that you want to close.
Swipe up on the app's preview to close the app.
more on that from Apple, here.
Press the posBoss icon again to reopen the app.
For older iPads that still have the home button:
Click the iPad’s Home button on the iPad to display the main screen.
Press the Home button twice again quickly to bring up the list of open apps. Scroll across (if needed) and locate the minimised posBoss screen. Swipe upwards on the minimised posBoss screen to properly close out of the app (as below).
Press the posBoss icon again to reopen the app.