Star Health And Allied Insurance — couldn't able to claim because of non disclosure

My mother recently undergo surgery related to uterus. We found out only when ahe went for q routine check up. Doctor suggested to have the surgery as soon as possible. When we reached out to star health, they said they cannot approve for the claim because we didn’t disclose this earlier, which we weren’t know until she went for for the check up. We are paying for the inaurance since 2012. We went to different hospital and paid for the bills from our pocket.