I replied via email but will post the reply here in case if someone has the same issue:
Please try testing this using 2 different accounts, only buyers have the Complete button so sellers can’t complete orders (and get the order amount to their balance) until the buyer confirms that the order is delivered. In the current version, orders can be delivered via messages (the message button is also located on the order page), please enable message attachments in HivePress/Settings/Messages section. We also plan to add the order revision limit and the order timeline (to deliver orders along with the Deliver/Complete confirmations) in future updates. In the current version, the process is:
1. Customer pays, a new order is created
2. Once the order is paid (it gets the Processing status), the vendor gets a notification and can start working on it
3. Vendor delivers files via messages or asks any extra questions via messages before the delivery
4. Vendor marks the order as Delivered (the manual delivery option should be enabled for this in Settings)
5. Customer gets a notification, then accepts or rejects the delivery