As an update, it seems that the customer that orders but doesn't trigger notification (PayPal payment goes through but no emails saying order came in get sent by PayPal or the store) has been checking out as a guest.

This doesn't sold the code in comments issue but could this be the reason for failed notifications? They have an account but don't use it when they order. But they use same email etc.

hello,

I only edited a file on System/Localization/Languages Definitions/ mail_account_create   text_activate file

Can you be more specific? Which file exactly on email template you mean?

I mean Design > Email templates

Hello.
Did you modify the Email Template?

hello,

I only edited a file on System/Localization/Languages Definitions/ mail_account_create   text_activate file

Can you be more specific? Which file exactly on email template you mean?

Hello.
Did you modify the Email Template?

Hello.
Login to the AbanteCart demo and make sure all form settings are same as default shopping-cart-demo

Hello Sir,

I already compared my settings with default demo panel and everything is same. I'm so confused  . maybe there is something wrong in the template it self?

Your support is highly appreciated 

Thank you...
G.O.