Check your location card in Business Central to see if you have any of the warehouse requirements enabled. If so, you will need to use WMS Warehouse with warehouse receipts, put-aways and picks.
WMS Standard can only be used with sales & purchase orders if all of those warehouse requirements are disabled.
If you want to mix and match with some requirements enabled and others disabled, that would require Warehouse Insight Advanced.
Note: Please check with your Business Central partner before making any changes to the warehouse requirements in the location card.