In-network provider sued Patent for Balance Bill self-funded Erisa

I am at a loss on this, in-network provider successfully sued patient for balance bill in state court despite denial of benifits with non-liabilty and both appeals being adminstratively denied for improper billing with non-liabilty of enrolle. Lawsuit was for breach of oral contract but the written ERISA contract had a hold harmless, and included language to prevent any form of out of network contract unless the provider informed the patient in writing services would not be covered under the plan (they did not). The judge ruled as if patient had insurance and would not correct to state it was Self-Funded ERISA, would this be a cause?

I'm confused. The provider was in-network - check. However, the claim for benefits was denied, and the patient went thru two appeals, both denied. I don't understand what "denied for improper billing" means? As in, the provider used the wrong ICD-10 code and that ICD-10 code happens to be a non-covered benefit? Need more details.