I’m having issues with previous customers accessing their invoices. Every time I click on the invoice it’s just a gray blank screen. I’ve uninstall the app & reinstalled

Hi there, @centersetplumbin. Thanks for sharing the steps that you've taken to address the issue.

Since you're still getting the same results after uninstalling and reinstalling the app, I'd recommend contacting our QuickBooks Support Team. This have the available tools to check your account and provide you with a fix. Here's how to connect with them:

1. Sign in to your QuickBooks Online company in a web browser.
2. Click Help (?).a
3. Select Contact Us and choose a way to connect with us:
   • Start a chat with a support expert.
   • Get a callback from the next available expert.

In the meantime, I'd suggest creating invoices in QuickBooks through a web browser. 

In addition, you can personalize the appearance and layout of your sales forms. Here's an article for your reference: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If there's anything else I can help you with, this thread is always open for more queries on invoices and other QuickBooks-related matters. Have a wonderful day.