You do not TRY to claim, there is a set procedure, follow that within the time allowed and you are guaranteed to get a refund.

First of all use the 30 day money back guarantee, link on every listing on right hand side, DO NOT waste time trying to deal with seller, who can ignore you or make unenforceable promises.

i just hope you never get in this situation again, but using ebay correctly the buyer will always win.