Refused to pay for faulty/damaged heatpump

Our heatpump stopped working and when my husband called Outsurance, they called a plumber to assess the fault and later on Outsurance said that the heatpump is not covered under the insurance scheme. I could not believe that. Please confirm if that is the case and your reasoning behind that. We have been happy with Outsurance and we stayed with you even when my company was offering cheaper rates. If you are going to have exclusions that are unfair, then we will have to reconsider who we are covered with.