You ran a full-page capture on a very long page and the resulting image ends abruptly before the bottom.
This is the designed limit, not a failure. Full-page capture scrolls the page and stitches frames into one tall image, and it stops at 60 frames, roughly 60 viewport heights, telling you when it truncates. Sticky and fixed elements such as headers are hidden after the first frame and restored afterwards, and capture paces its internal screenshot calls so long pages complete reliably up to the cap.
If the page was cut off, capture the remaining sections individually with region capture, or capture the specific section you actually need. For most pages the 60-frame limit never comes up.