Invoices not sending

Hi

I continue to have issues with invoices being sent every month.

This month is the worst I've ever had.  Of the 44 invoices I sent (through MYOB directly and not outlook) 12 of them have appeared not to have been sent at all.

I've even tried sending them twice and nothing. 

This is very frustrating.  I've checked the email sent in both desktop and online browser and they are just blank.

Anyone have any ideas why this is happening as it's very frustrating.

Thanks.