BPA external template for-each-group not working

Hi experts, we are in the process of implementing the iReceivables module for our ciutomers. We are trying to enable the invoice print functionality from the print button. For that we have defined an external BPA template, we have a complex grouping to be followed at the line level. We tried the for-each-group syntax in the rtf but it doesn't seem to help. Has anyone faced this scenario before? Please help with an rtf or sample code, I am attaching a sample desired invoice format for your kind reference.