
I tested this in 27.1 in a clean sandbox. When I select the Description on the Sales Line, Business Central automatically fills the Item No., Quantity, Unit Price, Line Amount, and the totals at the bottom. Because of that, the behavior you are seeing (totals staying at 0) is not standard for 27.1. It is most likely caused by a customization/extension in your environment. Also, please double-check that a Unit Price is defined on the Item card. If the Unit Price is blank on the Item, the line amount and totals will remain 0 even though the item is validated correctly.
If you can reproduce the issue in a clean CRONUS sandbox without any extensions and with a Unit Price set on the Item.