Missing squiggly lines and autocorrect

I get this thing sometimes where either I restart my Mac or I hit some accidental key combination and misspelled words stop autocorrecting and the squiggly lines disappear from under words, even when I have autocorrect - so far as I can tell - ticked in the appropriate menu. Anyone tell me what I’m doing wrong?

If by auto-correct you mean Edit/Spelling and Grammar/Check Spelling While Typing, then try toggling off page view mode. There is a known bug that can cause spelling and sometimes also symbol substitution to disable with that on. We don’t yet know why this is happening, we’ve been receiving scattered reports ever since an OS X update last summer, but there doesn’t seem to be anything in Scrivener that could be causing it, and these reports often indicate spell check can fail in other applications as well. Make sure to keep up to date with OS X, it could be eventually Apple will fix whatever broke.