Does it get the whole page, or just what’s on the screen?
Snagit apparently doesn’t “scroll the screen down” when you hit the bottom edge, so you’re limited to what’s visible when you frame the capture window.
Good news is, you can choose specific portions of the screen, frame them, and capture them.
But if you’re shooting to capture an entire webpage, try some of the other options suggested in the thread (including some free options).