Hello, StashVSP. Let me provide additional information about opening closed purchase orders.

The reason you're only seeing the Mark as Closed option instead of Mark as Open when opening a closed purchase order is due to the way the purchase order was closed. The Mark as Open option is only available for purchase orders that were manually Marked as Closed.

For purchase orders that were automatically closed due to being linked to a bill, the Mark as Open button will not be available, and only the Mark as Closed button will appear. While the Mark as Closed option remains visible, it will not perform any action since the purchase order is already closed. In this case, you’ll need to manage the linked bill first.  

Let me know in the comments if you have follow-up questions about managing your purchase orders.