My old invoice refused to open, what can I do?

Let me help you reopen your old invoice, boazuka.

May I know if you're referring to a paid invoice? If so, simply unlink the payment. Here's how:

1. Go to Customers & leads and choose Customers.
2. Locate and click the customer's name with the old invoice.
3. On the Transaction List Type dropdown, select Invoices.
4. Hit Edit beside the closed invoice and click the link payment on the upper right.
5. When the payment window opens, select Clear Payment. Then, hit Save and close.

However, if this isn't what you meant, I'd appreciate it if you could send us a screenshot of your concern to see what invoice you're referring to. From there, we'll know how to give you an accurate resolution.

Additionally, check out this article to help you personalise and add specific to your sales forms: Customise invoices, quotes, and sales receipts in QuickBooks Online.

Comment below if you have further questions about managing your invoices. I'll be around to assist you. Stay safe!