iOS notification when invoice viewed

Previously, when I signed up with QuickBooks Self-Employed and downloaded the corresponding app, I used to get a notification when the client had opened and viewed the invoice - something like " (Client's name) has viewed your invoice - one step closer to being paid"

About a month or two ago I transferred my phone data over to a new iPhone. While the app works fine, I no longer received the 'viewed your invoice' notification, and cannot find any solutions in settings or on QuickBooks Community at how to get this back? It was a really useful feature for my work, so I'm keen to set it up again!