SharePoint Server Subscription Edition AMA

Hi Marshall, are you using the Edge browser locally on your server hosting SharePoint? If so, you're likely running into User Account Control elevation issue. By default, Microsoft Edge will work with UAC to strip out the local administrator permission from your security token, so SharePoint Central Administration may not recognize that you're a local administrator. There are two ways you can address this:

1. Close all of your Microsoft Edge web browser instances, then launch the SharePoint Central Administration shortcut from the Windows Start menu. This will ensure Edge is launched in a way that doesn't strip out your local administrator security token, and you should have full access to all SharePoint Central Administration functionality.
2. Launch the Microsoft Edge web browser from a different computer than the one hosting SharePoint Central Administration.  UAC doesn't work across computers, so it won't be able to strip out your local administrator security token when browsing to SharePoint Central Administration on a different computer.