My invoice button has completely vanished from my Home Screen and I’m completely unable to send an invoice

I see you can't send an invoice in QuickBooks Online since the invoice button disappeared from your home screen. I commend you for the basic troubleshooting steps to rectify the issue.

If you have followed these steps and the issue persists, I recommend reaching out to our Customer Care Team. They have the tools to access your account securely and can conduct a thorough investigation to identify the root cause of this issue as soon as possible. Here's how:

1. Open your QBO mobile app.
2. Click the ? in the upper right corner.
3. Select Help and Support.
4. Tap the Contact Us button.
5. Enter a brief discussion with your concern, then click Continue.
6. Then select Callback.

You can contact us from Mondays to Fridays, 6 AM to 6 PM PT, and Saturdays, 6 AM to 3 PM PT.

In the meantime, you can use your mobile browser to access your account rather than within the app. If you use an iPhone, access it through Safari and Chrome or other available mobile browser for Android. You may see this article for additional information: QuickBooks Online access for mobile devices.

Here's an article that can guide you further in customising your invoice template and sales form delivery method on the mobile app: Customise invoices on the QuickBooks Online mobile app. 

For additional concerns about managing your invoices in QuickBooks Online, don't hesitate to post them here in the Community. We're always available and willing to lend a hand to your queries. Have a great day ahead.