The switcher needs access to a specific rule that the app will add.
The switcher will enable or disable the rule that blocks osu!'s access to the internet, but it can't do so without administrator access.
-Open the .exe file "osuoffline.exe"
-Allow administrator privileges
-Press "Add Rule" button
-Find and select your osu!.exe file
-Press "Switch Mode" button to switch to offline/online mode
-Enjoy!
If you're paranoid that the rule created is correct, please check by checking the firewall itself. Otherwise, you can start using the switcher.
More details in the section below.
-Open windows firewall through control panel
-Press "Advanced Settings"
-Go to "Outbound Rules"
-If you see the rule "osuoffline", right click it and press "Properties"
-Once in "Properties", select "Programs and Services".
-You will see your directory in the "Programs" section. Check if this directory leads to your osu!.exe file.
-If it does lead to your osu!.exe file, then you are now allowed to use the switcher. Enjoy!