If pressing the home button has no effect, guided access mode is on. To turn off guided access:
Triple click the home button.
Enter the passcode you set.
Tap End in the top left, you should see the text Guided Access Ended.
Now guided access mode will be disabled. To restart SinePoint Pro:
Double click the home button to get to the App manager.
Swipe up on SinePoint Pro card to close it.
Now to start SinePoint Pro again with guided access enabled:
Tap on SinePoint Pro from the App list.
Wait for SinePoint Pro to load your site details.
Triple click the home button, you should see Guided Access Started.