Refund declined

I purchased a Paint Zoom spray Gun. The instructions and videos on youtube mentioned nothing about the paint needing to be a specific viscosity. I used the paint i had and it was too thick. Went to builderswarehouse and explained what I needed paint for, they gave me their thinest paint, it was still to thick for the gun. Diluted the paint by 30% and although it spray abit it was still not effective. Received and email after returning saying that there was visible damage to the spray gun and that it would be returned to me as refund was declined. This is pathetic since I reported the issue hours after receiving the gun. I will post review and all social media platforms and will not rest until I am refunded.