Firstly make certain that the folder you have the mod in is not write protected. Later versions of Win 10 & Win 11 like to write protect a whole lot more locations in then before.
Second make sure your AV software isn't doing protection shenanigans either. AVG and Mcafee are both know to cause this sort of issue, if the mod folder is not set as an exception, and i wouldn't be surprised if others did the same thing. Stopping low level text tools, and direct commands from executing changes while high level programs get automatic exceptions is more secure, but like in our case annoying.
Thirdly, are you modifying the correct value in the correct file? Several values are used in multiple places but have different context depending on location.