@KjShepherd I have been working on a SharePoint 2019 server recently as a test/training resource at my work. Each time I would go to a site's homepage it would not show the top SharePoint Bar or allow me to make changes, despite my account being a "Full Control" Administrator. I found the issue was my SharePoint Central Administration URL did not match my IIS bindings. Below is what I did to fix the problem for myself, hope it helps you.
Update Web Application Binding in Central Administration:
To change the binding in SharePoint Central Administration, navigate to Application Management > Web Applications > Configure alternate access mappings. Click the Internal URL you wish to modify. (The SharePoint – 80 Web Application is typically used by default, which should reflect http://SERVERNAME.) Modify the URL protocol, host, and port to reflect what you are using in your IIS, then press OK.
To verify the change, navigate to Application Management > Web Applications > Manage web applications. The SharePoint – 80 URL and port should now reflect the change you have made.
