iPad6,11 J71tAP 12.4 unknown IV and Key

[flyingbird]

NSURL *IPSWURL = [NSURL URLWithString:[NSString stringWithFormat:@"https://api.ipsw.me/v2.1/%@/12.4/url", [apnonceDevice getModel]]];

You are using iOS 12.4 firmware. But iPad6,11 J71tAP 12.4 has unknown IV and Key https://www.theiphonewiki.com/wiki/PeaceGSeed_16G5056d_(iPad6,11)

Can you change to another iOS version, for example iOS 14.x

Thanks.