After waited for 3 weeks for a client feedback, He asked for a refund for a work he said it was OK!

[zeeson]

Hi guys, 
I worked with a client who after finishing any task will always told me to wait for a feedback from his team or CEO. 
We started with a paid test job and when he was satisfied, we agreed to start with the main job. 
I started the work on the 1st of June (a supposed one-week milestone). When I finished the work. He asked me to wait for feedback which lasted for 3 weeks. Then yesterday, he asked me for a refund that the work was useless for his business.
This is my 1st client on Upwork. 

[tlbp]

It could be a scam or the client could be legitimately unhappy with the work. Did you submit a request for the milestone payment? Did the client formally request changes using the milestone response process? 

If not, you'll have to decide if you want to pursue the money or walk away. 

[zeeson]

Since the work started, we do communicate using Skype which is fine since we are only using it for communication, file sharing, and submission. 
For the first two milestones which are a paid test job, he approved the work without me needing to submit formally using the Upwork submission form. 
So, for this current milestone, I can only submit through Upwork since he kept silent for a long time asking me to wait for feedback and my submission is 12 days today. And he never made any request until now. 
Can I wait for the next 2 days because I actually wasted a lot of time on the work since my belief is that it is going to be a long-term job as he promised.