QB Issue Resolution:

I don’t use QBO, so try what VP showed and click on the viewed sent in the status column, maybe that will bring up the email

push comes to shove, check the sent folder in your email client

Resolution for Issue 'How do I view sent invoices and emails?' available: Yes (Solved).
Source: Intuit Community forum.

How do I view sent invoices and emails?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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