Your site's shiki.maxBlocks option limits how many code blocks a document highlights. A block past that count shows its code without colors, still with Copy. Move the extra code to another document or remove blocks you no longer need.
The limit is a preset option, not part of the Markdown. If you own the site, choose the count when you register the preset and pass its plugins to the linter too:
import comarkUi from "comark-ui/html";
import { lint } from "comark-linter";
const preset = comarkUi({ shiki: { highlighter, themes, maxBlocks: 50 } });
const issues = await lint(markdown, preset);With this setting, the first 50 blocks your highlighter knows the language of get colors and later ones show plain. With no maxBlocks option, the preset does not limit the count.