What type of attorney do I need to fight a denial of life insurance claim?

My son had life insurance through his employer. His policy was for $50,000 basic life and an additional $50,000 supplemental life. Upon his death in July 2022 I filed a claim. The insurance company paid $50,000 for the basic life and only $20,000 supplemental life. I was told that for him to be eligible for the full $50,000 supplemental insurance he would have to provide proof of insurability. At no time was he informed that proof of insurability was required. I have filed two claims with same result. Are they required to pay the additional $30,000?