Just started using POS this week and we are having problems with the system advancing to the submit signature page. We can see in the background when the card has been approved by the green check icon appearing but the screen will not advance on its own. We have created a work around by hitting the home button on the iPad and then reopening the Shopify POS app. When the app is reopened, the signature screen appears.
That is something that should obviously never happen. I believe it is a bug that occurs if you happen to get a notification during the authorization. The iPad thinks the app is backgrounded at this point. To fix this: Press the Home button on your iPad to background the app and then bring the app back. You should should see the signature screen at this point. We will be releasing an update to fix this issue completely next week, although it happens very rarely.