While working with integrations for Oracle Fusion Order Management Cloud you may encounter this error DOO_ORCHE_PROCESS_ERROR. This Error is seen when calling the order fulfillment response service https://(yourdomain.com):443/fscmService/OrderFulfillmentResponseService
The reason for this error is that the order is not in the state to receive the response. Mostly an Order should be waiting for a response from and external system and for this there has to be a WAIT step added to receive the response and progress the orchestration further.
Validate the Order and the order orchestration should be in wait state. If not modify the orchestration process to add a wait step after a call to external system is made.
Once you add the wait step you can test the order fulfillment response again and it should not give the DOO_ORCHE_PROCESS_ERROR error.