Mom's life insurance company is requiring an autopsy report we never got. They've been sitting on the claim for 4 months. What now?

My mom passed in early January. She had a $250k term life policy that named me and my brother as beneficiaries. We submitted everything they asked for - certified death certificate, claim forms, the original policy doc - in late January.

It's now May and the carrier is still telling us they need "additional information." The latest stall is they want a copy of the autopsy report. Mom died of complications from a long illness, hospice was involved, the hospital didn't do an autopsy. Her primary doctor signed the cause of death on the certificate. I told the claims rep this and she said they'd "review it" and call me back. That was 3 weeks ago.

Is there a legal time limit on how long they can drag this out? My brother thinks they're hoping we just go away. The policy was active and paid up for 18 years. Has anyone been through a stall like this and got it resolved?