You are creating a stock movement, meaning adding or removing quantities to/from a product, from the Advanced Stocks grid, and when validating, a popup message is displayed: 'The label is not valid'.
This message informs you that no option has been selected under 'Label'. And for a very good reason... there are no options available, the list is empty.
The menu is empty because the labels are not setup in PrestaShop backoffice > Stock > Configuration > Stock: Stock movement labels
You will therefore need to create these labels to make them available in Store Commander.