The first domain listed in your question has the wp-admin slug, the 2nd doesn’t. You shouldn’t be making that change. Hopefully it was just a typo, however if that’s what you’re actually doing that is likely your problem.
Also, you should be changing all instances of the old domain http://20.210.236.41 to the new domain WITH SSL https://mostmarv.com/. That way you don’t need to use any SSL plugins.
If you can use WP-CLI this will work: wp search-replace http://20.210.236.41 https://mostmarv.com
Another option is to make the change in the dev server backend settings, download that db and then upload it to the new site.
One last option to get you up and running would be to add these lines to your wp-config.php file:
define('WP_HOME', 'https://mostmarv.com');
define('WP_SITEURL', 'https://mostmarv.com');
These 2 options could let you at least get the site live, but could cause a lot of problems though because WordPress uses the URL string an many other places thoughout the site. So you’re better off using WP-CLI or other software that will search for every instance of the older address or URL.
TLDR : Just changing your home and siteurl is not enough to completely transfer your site from one domain to another. You need to find all references to the old address.