[A] If MRP report is showing "0" in to be ordered quantity when MSL is ticked, then check the minimum stock level of that product as shown below.
[B] As you can see minimum stock level is not define for that product hence to be ordered quantity is showing as "0"
[C] In order to fix it add the minimum stock level for that product from inventory module
[D] Click on the below link which will help you to understand how to edit item/product details - https://intercom.help/tranzact-ebbdf0244a30/en/articles/3629992-how-to-amend-an-item
Keywords - to be ordered is 0, MRP showing wrong info