Hi there, @meowens07.
Let me share some troubleshooting steps, so you're able to access the mobile app in your device.
To start, let’s ensure you download the QuickBooks Self-Employed (QBSE) app based on the device you're using. You can uninstall and download the app from here:
Then, 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:
Let me know if there's anything else you need help with. I'll be here to help you some more. Have a great day.