Going round and round between insurance and hospital

My husband has had gastric issues and went to Johns Hopkins for a colonoscopy. The hospital took our info and got a pre approval from insurance, then scheduled a date. It’s been a year now and we keep going in circles. Hopkins first sent a $5k bill which showed insurance covered nothing. So I called an Hopkins said they submitted the claim, but nothing came back. So then I get on the phone with insurance, and they claim that they didn’t receive a claim to process. So I call Hopkins back to let them know, and I request that they re-process the claim. For several months I’d get the same bill, and I’d make the same calls between Hopkins and insurance. Finally, after a few months one of the charges went through and insurance covered $ 700. But for the remainder, it’s the same story. I get the bill and nothing is covered. I call the hospital and call the insurance. It’s been almost a year now of going in circles.

I did see on this subreddit a recommendation to contact the attorney general’s office. So I filed a claim with the Maryland office. It’s been around 6 weeks now and I haven’t heard anything from them.

I don’t know what else to do. The bill has now gone to collections and I can’t seem to get this resolved. Any suggestions?