The most probable reason behind this may be a blank Branch Code field for that particular item or entire production order.
No need to alter production order for solving this problem. Just go to Material Issue Worksheet, select template and click on OK button to open Item Reclass Journal.
Remove the Branch Code filter by clicking on red cross button before the filter. It will show all the records having blank Branch Codes.
Assign Branch Codes to all the rows the proceed as usual.