Quickbooks software is no longer sending emails to customers, I receive the BCC email of the invoice and it states it has been sent to the customer but they dont.

I know how you want the invoices to be sent to your customers without any issues. We can perform some troubleshooting steps to fix the issue, support-ajda.

There are times that the browser is full of frequently accessed page resources that cause some unusual responses. To isolate this, you can try logging into your QuickBooks Online (QBO) account in a private window (incognito). Here are the shortcut keys:
 

• Press Ctrl + Shift + N (Google Chrome).
• Ctrl + Shift + P (Firefox).
• Control + Option + P (Safari).
  
  

Once signed in, you can try resending the mail and check if your customer already received it. If so, return to your default browser and clear the cache to speed up the loading process. Every so often the cache becomes overwhelmed with older data which can potentially cause viewing and performance issues. Clearing it will refresh the system, and you'll be able to work with a clean slate. However, if the issue persists, try using other supported browsers. 

However, if the above steps don't resolve the issue, you can contact our support team so they can investigate further. Aside from that, they have the tools to pull up your account in a secure environment.

You may want to take a glance at how to record sales transactions in two ways. To give you complete details on the process, consider reading this article for your guide: Record Invoice Payments In QuickBooks Online.

Any questions in your mind? You can always message me below if you need further help from us.