How to reopen a closed PO detail line
To reopen a closed PO detail line, you must first make sure the overall PO isn't closed. To do this, access the 'Header' tab of the Purchase Orders screen and locate the status field. The status needs to either be 'Opened' or 'Printed'.
After verifying the overall PO isn't closed, flip to the 'Details' tab of the PO and locate the line in question. Scroll all the way to the right and you should find a 'Line Status' column. Clicking into that field will allow you to change the status of the line.