2697923 - Error DEC_TAB_EMAIL_SENDER Selected email template is not valid for output type PURCHASE_ORDER

You are creating a custom email template which is a copy of the standard one " MM_PUR_PO_DEFAULT_TEMPLATE ". When you try to assign this custom template in Output Parameter Determination App, you get the following error:  "DEC_TAB_EMAIL_SENDER (Expression)  : Selected email template & is not valid for output type PURCHASE_ORDER. "

SAP S/4HANA Cloud Public Edition

SSCUI,  DEC_TAB_EMAIL_SENDER, MM_PUR_PO_DEFAULT_TEMPLATE, Selected email template & is not valid for output type, PURCHASE_ORDER, YY1_MM_PUR_PO_TEMPLATE , KBA , MM-FIO-PUR-PO-2CL , Fiori UI for Purchase Orders (Public Cloud) , MM-FIO-PUR-PO , Fiori UI for Purchase Orders , Problem