Except this doesn't work for banned Nintendo Switches. And that's what this is about.I had the same problem and the best way for me was nintendo support, you just need a nintendo account, then go to the section parental control and click in forgot parental control pin, it took me 10 minutes and I got my masterkey, easy and fast
Need it for 16.0.0, doesn't work for now
What is the deal with v4 (Switch 8.0.0+)?
Nintendo has changed the algorithm to require a unique device ID that is stored on the console that can be difficult to obtain without exploiting the console in some way.
The device ID can be derived from fuses or obtained from PRODINFO on the Switch.
This limits the practical usage of the generator on these firmwares, as if one is able to obtain the device ID there are likely other ways to disable parental controls.
There is currently no known way to derive/obtain the device ID through trivial/visible methods.
This is cool for people who forget their PC passwords and for kids who want to outsmart Mummy & Daddy! (I salute you kids!)