How to proceed after insurance denial

My husband (32 M) recently started getting tremors and sometimes has really bad flare ups.

He scheduled an appointment with the doctor who ordered blood tests. The blood tests were normal so they prescribed medication to help with the tremors.

The blood tests were normal, so the doctor wants to get an MRI done. They got authorization from the insurance company, and the MRI was scheduled with the provider at one of the provider’s hospitals.

We just get a call today (3 days before the MRI appointment) saying the insurance is denying the MRI location because they don’t think it should be done in a hospital. The provider wanted to try scheduling at an outpatient facility, but they are booked out until November and we’d really like to know what’s going on.

Is there anything we can do to get insurance to cover the MRI at the hospital? I just don’t understand why the building the equipment is in matters. Who do I need to speak to at the insurance company?

Insurance company is Cigna.