Custom background color not showing up on mobile/incognito

Site URL: https://www.delicatehammerstudio.com/tributary-collection

Hi, I have custom CSS to change my background. Everything appears to be working, except when I'm incognito and on mobile on page load. Once I refresh, the CSS appears to be working. Any insights or help would be appreciated. 

Password is DHVIP2021

And the custom code used on this specific page's Page Header Code Injection is below:

<style>
.Main {
background-color: #212931 !important;
}
</style>

Design > Site Styles > Disable Ajax Loading

Thank you! That worked