If nothing helps, then there can only be one conclusion - your Windows is not in order, something is damaged, or another possibility - if you are not an administrator, you do not have rights to change these settings and the real administrator has turned them on.
I remind you - the fact that you are the only user of this computer and also that you have assumed the username Admin or administrator does not automatically give you administrator rights.
And one more observation - namely, there has been a situation with some versions of Windows that if you have turned off UAC, even if you run a program or app as an administrator, it does not help, your rights still remain as normal user rights. So you can try what happens if you turn UAC back on if it is off. But don't forget to Restart your computer after doing this.
Of course, there is also the possibility that some program or app turns it back on. This can happen if a program or app has a corresponding option in the settings and is configured so that this app has the right to show notifications. In this case, this right to display notifications must also be disabled in the settings of the corresponding program or app. And it should be mentioned that in reality there are quite a lot of such programs and apps that are not subject to Windows general settings.
But it's quite likely that Windows itself is actually damaged.
