Simple Classic Theme (fully supports Windows 8.1, 10 and 11)

Hi, first of all, sorry if my issue has already been discussed in other post. I tried to follow the guide yesterday but I could not properly install the application because the mid left "install" button was gray out. Anyway,that's not the foremost issue, although it would be nice if I could solve it, the main problem is that after failing to install it, my windows explorer stays exactly the same but with the font of w98. Same happened with browsers, now the font in the search box for example is a little bit different than the one previous installation. There could be other apps that changed its font. For the record, I don't have ltsb or ltsc, I've tried reseting the font configuration in control panel and I've also tried clear type. Any clue about what could be the problem? Thanks for the help.