I am having a similar problem. My header jpeg doesn’t show up in IE. I have tried posting this a few times, but each time, the topic gets marked “resolved”
Again: I am using the default theme, and my page is https://www.kelbournewoolens.com/blog/. I saved a new header image over the original kubrickheader.jpg and my image appears on some browsers, but not all. For example, it works on my macbook in safari and firefox, as well as an old pc that runs linux and firefox. It was tested on Internet Explorer on two different PCs and no image appeared, but did appear on the same computers on Firefox.
I asked the person on the PC using IE to view the page source and copy and paste the image code into a new browser window: https://www.kelbournewoolens.com/blog/wp-content/themes/default/images/kubrickheader.jpg and she said nothing happened, but that link leads to the header image on my computer.
In the general settings, I do not have anything written in the blog title or tagline.
I have also tried saving a new image name in place of the kubriheader.jpg and replacing the code with that name, but nothing there, either. The main website is built in dreamweaver, with all blog files saved within. Whenever I change anything, I update in the main wordpress page and “put” from dreamweaver.