Email advice notification not sending out emails

Hi,

so we have enabled email advice notification for a paycycle and configured the email address that will receive this notification. however, we have the below scenario:

On March 1, a payment was made to vendor, lets say, AAA. An email advice was sent to the email id.

On March 2, a payment was also made to vendor AAA and no email advice was received.

On MArch 3, a payment was made again to vendor AAA and an email advice was sent to the email id.

My question is, are there criterias considered when sending out the email? Is it looking for the status of the voucher? or in the payment table? Coz we can see that everyday there arepayments made for this vendor and yet there are times that the email notification is sent and there are times that did not.