FNB building insurance

I bought a house, 4 months in there's leaks from all the rain, the building insurance won't fix saying it's neglect, its not my neglect why don't they get the seller, lawyer and agent to sort this out? every month the debit order goes out now 6months in it's getting worse as the rains are heavy. Why did the bank insure a house like this and not inform me of this issue? Seller did not disclose, as buyers we ask and never climb to check the roof, is this fair?