It doesn’t matter whether you have an insurance claim or not – the primary issue is whether a defect in the common property caused the damage to your property.
If it did, then the OC is responsible for fixing the damage. They have to lodge the insurance claim, and if it is refused then they have to pay anyway.
As I said above, get someone in if necessary to write a report on what caused the damage, and assuming it is caused by a fault in the common property then advise the OC that they have to pay for it.