Why won’t our insurance pay out for a fault in building work?

The builder went bust before fixing the problem, but our policy covered that eventualityWe built a £49,000 annexe three years ago. Last year we found some bubbling in the external render, which the builder agreed to treat.There were various delays due to weather and cancelled appointments and then we received notice that the firm was in liquidation. Fortunately, the deal included “a guarantee in the event of the builder ceasing trading”, so we sent a claim to the insurers but t