Header not displaying correctly in custom theme

Here is what the theme is supposed to look like (this is a screencap from where wordpress previews the theme):
https://orlandocorporatemagician.com/images/wpscreencap.png

Here is how it is actually displaying:

https://orlandocorporatemagician.com/corporate-entertainers/

In the prior version of WordPress, the single post (single.php) would display header correctly, but not on the main blog page)…