Do you get a "splash screen", similar to the left one in my "signature" below, when starting the game since activating the mod? There is one thing to remember about LAA activation, in that it does not error if the "target" (SH4.exe) has its "Read-only" Attribute set. All will look normal as far as it's concerned. If MultiSH4 let you create a new Save folder though, that probably is not an issue, but you can double-check it by navigating into the game folder, selecting the SH4.exe file, right-click on it and left-click "Properties" at the bottom of that context menu. The "Properties" will open to the "General" tab, and at the bottom is the "Attributes" section, and just make certain the "Read-only" tick box is cleared. You can "Apply" that, or just OK it. While you are there though, you could also check the "Compatibility" tab, and set things similar to this:
you will have to experiment with some of those settings, depending upon your computer, video card and display. The Windows 11 version of that Win10 picture there might be slightly different, but the principal is the same. You might be able to leave the "Run this program as administrator" empty, but that "Change high DPI settings" button is almost mandatory, which that's what the top little window is, on newer equipment in Win10.