Self-funded insurance plans

My wife and I welcomed our first baby in March of this year. At the time we were insured by my company which has since dissolved (roughly 3 months after my daughter was born), and with it the insurance plan we paid so much towards. It was a small company and they provided us with a self-funded plan they built through Nova which insured us through Cigna. After unexpectedly being denied financial assistance by the hospital we’ve been watching the hospital bills climb for ~7months as the hospital slowly sent them to the insurance and got them back.

Currently we owe 5k after insurance, with 16k still pending insurance. After 6months the hospital is still sending the bills over to Nova, who now claims they cannot pay any of them. When I called and spoke to customer service at Nova they explained to me that it was a company-funded plan, and since the company is gone there is no money to pay with and they cannot help. We were covered at the dates of service, paid a lot of money to the insurance company, and now they are not paying for bills amassed in that time frame. Before I expend what little energy I have remaining I just want to know if there’s any legitimacy to what the insurance company claims. Some people I’ve gotten advice from have said that is nonsense and said contact Cigna directly (as opposed to Nova), but I’m not sure if like me they are just unfamiliar with this type of insurance plan. I fear the hospital will send threaten to send these bills to collections if we don’t send them to the financing institution like we did with the ones insurance already paid part of.

tldr: Company provided self-funded health insurance at time of my wife’s delivery, company dissolved after and the insurance disappeared with it, now 6mths later the hospital is still sending bills to the insurance who claims they can’t pay anything since the company is gone. Is this legit?

Thank you so much, it has been an overwhelmingly stressful year.