I have 2 primary insurance companies and one won’t pay a bill

I have 2 primary health insurances. About 15 months ago, I was 90% sure my company was going to go out of business. I landed a a job in consulting. I signed up for benefits at the new job ready to quit/be let go from the old job as they went into bankruptcy.

The consulting company put me on mostly 2nd shift kinds of things. The first job got capital investment firm to help out, and no layoff. I’ve been with both and managing until I figure out is there’s a future with job 1.

So, new job has been the health insurance I use. I’ve used it for everything. I got a colonoscopy. And a letter from new company insurance saying they need me to use primary insurance. I consider them the primary. New job health insurance refuses to pay the hospital bill now.

Has anyone dealt with this? How do I get the health insurance company I’ve been using all year long to pay the bill? Note: The deductible is met with job 2… and nothing on job 1’s bill. Insurance companies are talking to each other out there.