This is typically due to multiple Magisk managers being installed, if at any point, Magisk Manager was hidden, and then another Magisk manager was installed, you'd face issues as this.
@dadnammit you should first do is, uninstall all Magisk managers, hopefully you can find the hidden one, or at least you know the package name, if you did not rename the application when you hid, then it should be named settings.
If you have already applied patched boot, then reboot and just install Magisk Manager. and it should detect root.
You can confirm that you're rooted by doing
if you get su, you're rooted.
If you are on stock, then just install Magisk Manager and flash the patched boot.
Whatever you do make sure you only have a single instance of Magisk manager.