HR and ADP messed up and after 3 months, I still don’t have insurance

I turned 26 back in June and aged out of my parents’ insurance, and tried to enroll through my employer, but as I filled out the forms on ADP, I found out that I needed Proof of Loss of Coverage. I got that a week later and tried to finish filling our the paperwork, and ADP would just give me an error message and send me back to the home page, so I couldn’t submit any of the paperwork.

I contacted HR about the issue and was ignored. The emails I sent went unanswered, and none of my calls went through. After speaking to my supervisor, he gave me the contact information of someone else in HR, and I was once again ignored for weeks. By the end of July, I finally got in touch with someone, and they said they could fix the issue. They did not. I sent them a message saying that the issue had not been resolved, and nothing had changed, but they ghosted me, even after I’d sent multiple messages trying to get back into contact with them.

After a month of this, I approached my supervisor again, and within hours, HR was “looking into the issue.” This was at the end of August, a full two months after I started trying to enroll.

It took another two weeks for someone in HR to finally fix the problem and get me enrolled, letting me submit my documents, resolving the issue, and finally getting health insurance. Or so I thought.

As it turns out, my coverage doesn’t begin until October 1st, a full 15 weeks after I initially tried to apply.

Unfortunately, during those final two weeks of HR shenanigans, I was taken by ambulance to the ER, and have since been hit with a heavy bill, which insurance won’t cover because my coverage doesn’t start until October.

I’ve reached out to HR again to try and get them to change my enrollment date to July 1st or August 1st, when I should have had insurance, and would have been covered if they’d simply done their job. This time, they got back to me within 3 business days (kudos to them), and told me that they can’t change the date due to a “mandatory waiting period,” which seems like a bunch of malarkey.

Can they do this? Do I have any options? Am I able to threaten legal action? Would I even have any grounds?