Sometimes it may look like the screen stalls because of network slowness. Do not load the order again. Instead, open another tab in Evergreen and do a search for a pending purchase order to see if the order has loaded.
Acquisitions -> Purchase Orders -> change state to “pending” in default search -> click search.

For more information see http://docs.libraries.coop/acquisitions/_search_for_purchase_orders.html#pending-order