When viewing individual customers information, the button which returns to main page disappears. Have to close down app every time.

Thanks for dropping by here in the Community, @leaftreeserviceds. I'll help with your concern so you can your get things back on track.

Clearing the data in your QuickBooks Online mobile app can help you resolve issues with it. This helps refresh the application and remove the common causes of screen freezing. I recommend that you try the following steps if you haven't already.

Clearing the App's data can be done on the app or on your mobile phone settings. I'll be providing the instructions below:

For QuickBooks Online app:

• Android - Select the menu at the top right and choose Settings. Then select Refresh Data and choose Yes.
• iOS - Select the menu at the top right and then choose Help & Feedback and then select Refresh Data and Refresh.
  
  

For visual reference, you can refer on the screenshot below.

In your Phone Settings:

• Android - From your phone setting, select Apps and then choose the QuickBooks App from the list. Click on Storage and then select clear data.
• iOS - Go to Settings and then click on General. Choose iPhone Storage and then select an app that's taking up a lot of space. To free up the storage without deleting the documents and data for the app, select Offload App.

I’m adding a link here where you can search for an article that will help you if you need some information or procedures while using QuickBooks Online. Help articles.

Don't hesitate to get back to me if you need further assistance with this. I'll be more than happy to help you get this sorted out. You can notify me by leaving a comment down below. I'll keep an eye for your response. Have a nice day!