Email is not sending after paypal payment is complete

Hi guys, I’m wondering why the COMPLETE ORDER email is not sending after the paypal payment is complete. Instead, I have to login in WordPress dashboard and mark the transaction to COMPLETE then the customer will receive the email.

I have a downloadable file in every product, how can be that will be automated? I mean I don’t need to manually mark all the transaction to COMPLETE so the customer can receive their EMAIL for them to download the file. Any idea guys? Or I’m just missing some set up in Woocommerce settings.

I did not do any customization, just the Woocommerce default template.

Thanks guys