Are you using Windows 11? You need to turn off the virtualization features so ThrottleStop can read and write to the CPU registers.
Disable Virtual Machine Platform and Hyper-V and ThrottleStop should work correctly. Delete the ThrottleStop.INI configuration file after you disable these Windows features and reboot. Post some screenshots if you are still having problems. The default turbo ratio limits, voltages and reported DDR speed can only be reported correctly with virtualization disabled.
If you need to run WSL2, you can no longer use ThrottleStop to undervolt your CPU. This used to be possible in Windows 10 but this is not possible in Windows 11.