I have a client that does not want the project anymore, and he requested a refund for 0$. He didn't pay anything until now. How can I clear this refund request, as there is no invoice to refund?
I'm sorry for the confusion, Costin.
It looks like this contract was opened and funded last October 2017. Since there was money held in escrow, the system had to automatically refund the money in escrow to the client's payment method. If you go to this page, you will see that the refund request has already been approved by Upwork.
For legal reasons Upwork isn't able to keep funds indefinitely. That's why a fixed-price contract with funds in Escrow will be closed automatically after 90 days of inactivity. Fixed-price contracts with money in escrow and no activity for 90 days will be considered dormant and will be actioned on. You may read more about dormant contracts on Section 3. Dormant Contracts of the Fixed-Price Escrow Instructions.