Homepage header

I have set up a new site (additional domain and will then switch over to when done) https://newsite.breamearlylearners.com/ as I am re-doing this for the organisation. I am really stuck on something that is causing me frustration! My homepage (https://newsite.breamearlylearners.com/) is set to static page (have set under reading setting) and I have put a header image in. However, it displays this header image on every page except the homepage! It seems to think this page https://newsite.breamearlylearners.com/wp-admin/customize.php?url=https%3A%2F%2Fnewsite.breamearlylearners.com%2F is the homepage, which is a blog page! It is all showing correctly under settings, but it keeps reverting to the homepage as a blog page! It is driving me mad! Can anyone help? I have tried several things including disabling plugins, deleting and adding a new homepage etc. I have also looked on other threads and no luck. Please help me!