Is anyone unable to access your customer list on a sales receipt or an invoice?

I'm having the same issue. 

Looks like it's fixed now.  

Hello there, damon.

I'll ensure to provide an update about the drop-down menu issues in QuickBooks Online (QBO).

At this time, we have an ongoing investigation into the drop-down menus that are not responsive in multiple areas of QuickBooks. Please know that our engineer is currently working on it. We appreciate your patience as we investigate this further.

For now, I recommend contacting our QuickBooks Support Team so that they can add you to the list of the affected users. This way, you'll get notified once there's a fix or an update about this issue.

Here's how:

1. On your company file, go to the Help menu.
2. Select Contact Us.
3. Enter your concern, then select Let's Talk.
4. Choose a way to connect with us:

• Start a chat with a support expert.
• Get a callback from the next available expert.

Please refer to this article for more details about the support schedule: QuickBooks Online Support.

Feel free to visit this handy article for future reference in recording customer payments:

• Record invoice payments in QuickBooks Online

Tag me in the comment section if you have clarification about managing your invoices in QuickBooks. I'm always here to help you.