You'll have to open the invoices manually to send them to your clients. To make the process easier, you can run the Open Invoices report to get a list of the transaction.
Just click the Amount link on the report, so you'll be prompted on the transaction. Then, hit the Save and send button so your client will receive the invoice again. But I get your point and its useful effects, and I'm sending your feedback to our developers.
For future help about importing and customizing QBO invoices, you can refer to the following links: