Laptop not showing in Sophos Central. Cannot uninstall

We have a laptop that has the Sophos Endpoint software installed, but it is not showing up in the Sophos Central Portal. We are trying to uninstall Sophos on this machine. Of course, it is telling us tamper protection needs to be disabled in order to uninstall. 

We have tried following this link: 

https://www.avanet.com/en/kb/uninstall-sophos-endpoint-protection-with-tamper-protection-enabled-windows/

in order to manually uninstall it. This solution fails, as it says Access Denied when trying to edit any Sophos registry keys. 

We have also tried following this link: 

https://techbast.com/2020/11/instructions-on-how-to-remove-sophos-endpoint-when-losing-tamper-protection.html

With the same  failed results. As well as following multiple Sophos community posts. 

Does anyone have a fix for this?