When you use the purchase requisition excel add-in to add lines and leave the financial dimensions empty, the line becomes invisible after you publish it. Even though the line is actually added on the header in F&O.

It is essential you see all the lines of your purchase requisition, as you need a representative situation in the excel add-in vs the actual data in F&O. So you need to see all the lines, all the time, even though the line doesn't have financial dimensions.