Hi Amatera! This happens because ACSG uses a custom window management system. When you minimize the tool, it turns into a small floating control bar (usually appearing near the bottom-left or above the taskbar).
To bring the program back to full size, clicking the Windows taskbar icon won't work by itself. Instead, you need to click the 'Maximize' button (the square icon) directly on that small floating window.
Check the image below to see exactly where to click:


Thanks!