We have to try partial credit memo for Magento 2.2.0 shop admin for below step:
1) Proceed order with default payment and Grand Total are €37.00
2) Create the Invoice.
3) Try to Credit memo with Adjustment Fee are €10.00
After refund, Order status set Closed status.
Order History:
Order Total:
And Credit memo button are not available in order history.
How to fix this issue....!