Ok, this is happened to me yesterday. I tried to contact the seller and also CS but fiverr compensates me with a level warning demotion. I suggest to not to do anything so you don’t get a bad situation like it happened to me because fiverr will tell you that bad review will never be removed. All you have to do is to leave your review to the buyer to, give him 1 star as well and leave a super big negative review, so the future client when they see that bad review they will read your review as well.
Here is my topic about this in case you would like to check Unfair demotion warning