I would call your insurance agent. If you need a new reference for an insurance agent then call Bender insurance. Nancy Bender does a great job and can help you. You should be able to explain and get a policy for vacant home. Many people purchase a home and then do work prior to moving in so you are not the only one.
I had a smilar problem with a home I owned and I solved it by talking with my agent on what I could do to get it fixed. Ideally you don't want to have your insurance canceled. They usually send you notices and give you a heads up prior to cancelation.