I'll provide information on why the mobile app says your account does not include access to the online mobile app. And, how to connect or login your QuickBooks account to a mobile app.
It could be you downloaded the QuickBooks Online app instead of QuickBooks Self-Employed app. That's the reason you're getting the message that says your account does not include access to the online mobile app.
I suggest ensuring you download the QuickBooks Self-Employed (QBSE) app. You can install the app using the links below based on the device you're using:
Once done, log in using the same username and password you enter when accessing your QBSE account on the regular web browser. For more information, I've attached some articles you can use for some FAQs about the product and if you want to create or attach a receipt to a transaction: