Neither tweeter was working? It is highly unlikely that they were both working prior to shipment and both were rendered inoperable during shipping. In short, there is no guarantee that is the problem. The seller is responsible for delivering operable speakers, you accepted the offer of replacement tweeters but for whatever reason, the seller hasnt been able to fulfill his/her obligation. If the tweeters come in, you install them and they dont work, what next? New crossovers?
I would ask the seller for a full refund.