FIRAuth *auth = [FIRAuth authWithApp:app];

 [auth signInWithEmail:@"email"
               password:@"password"
             completion:^(FIRAuthDataResult *_Nullable authResult, NSError *_Nullable error) {
               if (error != nil) {
                 if (error.code == FIRAuthErrorCodeSecondFactorRequired) {
                   FIRMultiFactorResolver *resolver = (FIRMultiFactorResolver *)error.userInfo[FIRAuthErrorUserInfoMultiFactorResolverKey];
                   // here the resolver is associated with the wrong app name see screenshot

                 } else {
                   result.error(nil, nil, nil, error);
                 }
               } else {
                 result.success(authResult);
               }
             }];