Legal Question in Landlord & Tenant Law in California

Your question makes no sense. I have never heard of a renter's insurance policy that did not cover damage from the landlord's negligent maintenance. If you really did have insurance, and it really was denied, and the denial really was legitimate under the policy, you would claim your damage first by sending a letter to the landlord demanding compensation. If the landlord refuses to pay, then you sue in small claims court if the loss is $7500 or less, and in Superior Court, if you need to collect more. In any case, if you were actually legitimately denied coverage, you definitely need to change insurance carriers.

Read your renter's insurance policy. I find it difficult to believe that any insurance policy does not cover the negligence of someone else. What did they tell you when you bought the policy?

If in fact there is no coverage, then if the landlord was negligent, sue in Small Claims Court which has a upper limit of $7,500.