Menu changes go live immediately, so this is almost always a cached page on the device you're looking at.
Try, in order: 1. Pull down to refresh the menu page, or reload it in the browser. 2. Check you edited the right branch — each branch has its own menu. 3. Check the item is switched on and, if it's scheduled, that it's inside its time window. 4. Try a private or incognito window to rule out an old cached copy.
If it still doesn't appear after that, contact support with your restaurant name and the item you changed.