Invoice Email not received

I attempted to send an invoice to my customer to test if they would receive it. I am currently using the free version of the cloud system to test its functionality, but unfortunately, the invoice email was not received.
Any suggestion, how I will fix it?

However, my receipt/bill was successfully sent and I received an email confirming it.

Any suggestion would be highly appreciated.

Thanks.

Invoice not received, using free cloud version. For a solution, check email settings, customer's email validity, and spam folder. Contact customer support if needed.