Hello
I wrote the following WIKI about the most frequent issues on MD04 and there is a section specific for this kind of issue:
Check the relevant information below:
Sales order/delivery number is not displayed
A sales order, delivery, quotation or SD schedule agreement is displayed on transaction MD04 without any reference to the document number. Error message “61111 - Selected function cannot be used for the element” is displayed when you try to open the element.
This is not an inconsistency. It happens when “daily requirement” or “weekly requirement” is selected for the availability check in the material master. More information about this system is provided on SAP Notes 70408 and 1649669.
The procedure from note1649669 should help you to find the sales order numbers.
BR
Caetano