Twenty Thirteen header does not appear on mobile apps

Gang,

I’m starting a site at https://billweissauthor.com/ using the Twenty Thirteen theme and the header doesn’t show up on my Android phone in any browser I try.

Sorry if this has been covered elsewhere, but I can’t find anything directly related in the search tool.

I did make sure my new header image fits the size requirements, but also tried it with the default header and have the same issue.

any ideas?

Thanks.