My customer is getting this error message when he is trying to pay us Error, you can try again, or come back later and try connecting then How do I help him?

Hi there, @accounting481.

I'm here to help get you and your customer back to business.

Your customer may be having technical issues within the browser so let's begin with letting them use a private or an incognito browsing mode to isolate the hurdle. This mode avoids Internet files that can affect browsing performance in QuickBooks like clicking the Pay Now button.

For Firefox, your customer can press Ctrl + Shift + P and Ctrl + Shift + N for Chrome.

Once your customer can pay the invoice from there, let them clear the web browser cache. It also boosts their browser's performance. Alternatively, they can use another supported browser to isolate the issue.

I've added a reference in case you met some issues with receiving customer payments in the future like how to resolve declined credit cards: What to do if customers can't pay their invoices online.

Please share with me how it goes by placing your comment below. I'll keep my notifications open. Take care.