magento2.3.1 – Magento2: Invoice and shipment emails are not going to the customer

I am using Magento2.3.1.
I have installed mageplaza SMTP extension and configured it with Send Grid details. I have completed all configuration and able to sent test email successfully.

After that I have placed a test order using COD and I received new order email.
After this I have generate invoice and shipment for this order from admin > Sales > Order section (without tick “Email Copy of Shipment” option).

My customer not received any invoice and shipment email.

Any one let me know what is the issue and “Email Copy of Shipment” option required to tick for notified to customer via email about invoice and shipment.

Please let me know is this any code issue or any process issue for generating invoice and shipment from admin.